INTRODUCTION — Type 2 diabetes mellitus occurs when the pancreas (an organ in the abdomen) produces insufficient amounts of the hormone insulin and/or the body's tissues become resistant to normal or even high levels of insulin. This causes high blood glucose (sugar) levels, which can lead to a number of complications if untreated.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain normal or near-normal blood glucose levels. Treatment includes lifestyle adjustments, self-care measures, and medications, which can minimize the risk of diabetes and cardiovascular (heart-related) complications.
This topic review will discuss the treatment of type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient information: Diabetes mellitus; type 2" and see "Patient information: Self-blood glucose monitoring" and see "Patient information: Hypoglycemia (low blood glucose) in diabetes" and see "Patient information: Lifestyle modifications in type 2 diabetes" and see "Patient information: Preventing complications in diabetes mellitus").
TREATMENT GOALS
Blood glucose control — The goal of treatment in type 2 diabetes is to keep blood glucose levels at normal or near-normal levels. Careful control of blood glucose levels can help prevent the long-term effects of poorly controlled blood glucose (diabetic complications of the eye, kidney, and cardiovascular system).
Blood glucose control can be measured by checking the blood glucose level before the first meal of the day (fasting). A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), although some people will have a different goal. A healthcare provider can help to determine this goal with the patient. Some people will need to test their blood glucose level before and/or after other meals during the day, and the frequency of testing can change as diabetes progresses. (See "Patient information: Self-blood glucose monitoring").
Blood glucose control can also be measured with a blood test called A1C. The A1C blood test measures the average blood glucose level during the past two to three months. The test is done by giving a small sample of blood from a vein or fingertip in a clinician's office. The goal A1C for most people with type 2 diabetes is 7.0 percent or less, which corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show figure 1). A healthcare provider can determine the A1C goal for an individual patient.
The average blood glucose goal (150 mg/dl or 8.3 mmol/L) is higher than the fasting blood glucose goal (100 mg/dL or 5.6 mmol/L) for several reasons. Blood glucose levels increase after eating. The amount and speed of the increase depend upon the type and amount of food eaten at a particular meal. The increase also depends upon the type and dose of diabetes treatment(s) used and the person's activity level.
Cardiovascular risk control — The most common long-term complication of type 2 diabetes is cardiovascular (heart) disease, which can cause myocardial infarction (heart attack), angina (chest pain), stroke, and even death. The risk of heart disease is estimated to be at least twice that of persons without diabetes. (See "Patient information: Preventing complications in diabetes mellitus").
However, persons with type 2 diabetes can substantially lower the risk of cardiovascular disease by quitting smoking, taking a low-dose aspirin every day, and by managing high blood pressure and hyperlipidemia (high cholesterol) with diet, exercise, and medications. (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and see "Patient information: High blood pressure treatment" and see "Patient information: Smoking cessation" and see "Patient information: Aspirin and heart disease").
Persons with type 2 diabetes are also at increased risk of developing eye, kidney, and nerve complications that can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. These complications can occur after many years of diabetes and are related to elevated levels of blood glucose over time. Complications can be prevented or delayed by keeping blood sugar levels as close to normal as possible and by carefully controlling blood pressure. Diabetes remains the greatest cause of blindness, kidney failure, and amputations in the United States and in much of the world.
DIET — Changes in diet can improve many aspects of type 2 diabetes, including obesity, high blood pressure, and the body's ability to produce and respond to insulin. Response to dietary changes depends upon the number of calories consumed, types of foods chosen, and the amount of weight lost.
For a person who is newly diagnosed with diabetes and who is overweight or obese, losing any amount of weight can reduce or eliminate the need for medications and improve blood glucose levels.
The American Diabetes Association recommends a low fat, low calorie, high complex carbohydrate diet. A dietitian can help to determine the optimal number of calories and fat for an individual patient. (See "Patient information: Weight loss treatments").
The following are general diet recommendations: Eat a lot of vegetables and fruits, at least five servings a day. Limit starchy vegetables (eg, potatoes) but eat as many non-starchy fruits or vegetables as desired. Choose foods with whole grains rather than processed grains. Consider whole wheat bread, brown rice, or whole wheat pasta instead of white bread, white rice, or regular pasta. High fiber foods can help a person to feel fuller sooner; 15 to 30 grams of fiber are recommended daily (show table 1A-1C). Eat a limited amount of red meat, and choose lean cuts of meat that end in loin (pork loin, tenderloin, sirloin). Remove skin from chicken and turkey before eating. Include fish two to three times per week. Choose low or fat-free dairy products, such as skim milk, non-fat yogurt, and low-fat cheese. Avoid high calorie snack foods, including regular soda, fruit punch, candy, chips, cookies, cakes, and full-fat ice cream. Use liquid oils (olive, canola) instead of solid fats (butter, margarine, shortening) for cooking. Fat should be limited to less than 30 percent of a person's total daily calories. For a 1500 calorie per day diet, this would mean about 45 g or less of fat per day, which can be counted using the nutrition information labels on most food packages (show figure 2).
For patients who are not able to lose weight with diet alone, a weight loss medication may be considered. Patients with type 2 diabetes who have a BMI greater than 35 kg/m2 can also consider a surgical weight loss procedure. (See "Patient information: Weight loss treatments", section on Weight loss medications and see "Patient information: Weight loss surgery").
EXERCISE — Regular exercise can benefit people with type 2 diabetes, even if weight is not lost. Exercise improves blood glucose control because it improves the body's response to insulin. (See "Patient information: Exercise").
Exercise does not need to be vigorous and it does not need to be continuous to produce health benefits; it can be broken up into three or four ten-minute sessions per day. The recommended goal is 30 minutes of moderate-intensity exercise at least five days per week. However, exercising only one or two days per week is better than not exercising at all.
PSYCHOLOGICAL TREATMENTS — Patients with type 2 diabetes often experience significant stress related to their disease and the increased responsibilities that come with it, including blood glucose testing, dietary considerations, exercise, healthcare provider visits, the need for medication, and the potential risks of complications. It is not uncommon to become depressed as a result of this stress, and this can make taking care of oneself more difficult.
Committing to new treatments and lifestyle changes can be difficult, and it is not uncommon to feel that the benefits of treatment are not worth the effort. Having an open and honest discussion with clinicians can help patients to understand their diagnosis and the need for treatment.
Involving family and friends can help people with diabetes to manage their disease by offering reminders to take medication, test blood glucose levels, and providing a ride to appointments. Family and friends can also give encouragement and support to eat a healthy diet and stick with an exercise plan.
Working with a psychotherapist or social worker can help patients with type 2 diabetes to cope with new responsibilities and worries. A number of studies have shown that patients who have psychotherapy in addition to traditional medical care have reduced stress and improved blood glucose control compared to patients who received only traditional care [1].
MEDICATION — A number of oral medications are available for the treatment of type 2 diabetes. A table of these medications is available in table 2 (show table 2).
Metformin — Most patients who are newly diagnosed with type 2 diabetes will immediately begin a medication called metformin (Glucophage®, Gumetza®, Riomet®, Fortamet®). Metformin improves the body's response to insulin to reduce elevated blood glucose levels.
Metformin is a pill that is usually started with a dose of 500 mg with the evening meal; a second dose may be added one to two weeks later (500 mg with breakfast). The dose may be increased every one to two weeks thereafter, up to a total of 850 mg twice per day.
Common side effects of metformin include nausea, diarrhea, and gas. These are usually not severe, especially if metformin is taken along with food and the dose is increased gradually. Patients with certain types of kidney, liver, and heart disease, and those who drink alcohol excessively should not take metformin. It should not be taken within 48 hours of any test that uses iodine-based contrast dye, and it should be stopped before surgical procedures. It is not recommended for patients older than 80 years unless kidney function testing shows that the kidneys are functioning well.
When to add a second medication — For patients who initially take metformin, a second medication may be added within the first two to three months if blood glucose control is not adequate. "Adequate" control is defined as an A1C level less than 7 percent for most people; insulin may be recommended if the A1C is elevated, especially if it is higher than 8.5 percent.
Sulfonylureas — Sulfonylureas have been used to treat type 2 diabetes for many years. They work by increasing insulin production, and can lower blood glucose levels by approximately 20 percent. However, they lose effectiveness over time. Sulfonylureas are generally used if metformin does not adequately control blood glucose levels when taken alone, but may be used first in people who have liver, kidney, or heart disease and in those who drink alcohol excessively. They should not be used by patients who are allergic to sulfa drugs.
A number of sulfonylureas are available (Diabinese®, Orinase®, Glucotrol®, Diabeta®, Micronase®, Glynase®, Amaryl®), and the choice between them depends mainly upon cost and availability; their efficacy is similar. The medication is in pill form and is taken once or twice daily.
Patients who take sulfonylureas are at risk of low blood glucose, known as hypoglycemia. This can cause sweating, shaking, hunger, and anxiety, and must be treated quickly by eating 10 to 15 grams of fast-acting carbohydrate (eg, fruit juice, hard candy, glucose tablets). Delaying treatment can cause the person to lose consciousness. A full discussion of hypoglycemia is available separately. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Insulin — In the past, insulin treatment was reserved for patients with type 2 diabetes who did not have adequate blood glucose control with oral medications and lifestyle changes. However, there is increasing evidence that using insulin at earlier stages may improve overall diabetes control and help to preserve the pancreas's ability to make insulin. Insulin injections may be used as a first-line treatment in some patients, or it can be added to or substituted for oral medications.
Insulin requires an injection by the patient or a family member/friend. Inhaled insulin is newly available, but its effectiveness in treating type 2 diabetes is still being evaluated.
Most patients with type 2 diabetes begin by taking one insulin injection per day, usually at 10 P.M. The dose can be slowly increased every few days, depending upon the person's first morning blood glucose level (which should be measured every morning before eating). Some patients will need additional injections throughout the day while others have a good response to only one injection per day.
Meglitinides — Meglitinides include repaglinide (Prandin®) and nateglinide (Starlix®). They work to lower blood glucose levels, similar to the sulfonylureas, and may be used in patients who are allergic to sulfa-based drugs. They are taken in pill form. These medications are not generally used as a first-line treatment because they are more expensive than sulfonylureas and are short-acting, so they must be taken with each meal.
Thiazolidinediones — This class of medications includes rosiglitazone (Avandia®) and pioglitazone (Actos®), which work to lower blood glucose levels by increasing the body's sensitivity to insulin. They are taken in pill form and usually used second-line, in combination with other medications such as metformin, a sulfonylurea, or insulin.
Common side effects of thiazolidinediones include weight gain and swelling of the feet and ankles. There is a small but serious risk of developing or worsening congestive heart failure in patients who use thiazolidinediones. Close monitoring of swelling is important to detect this condition.
Alpha-glucosidase inhibitors — These medications, which include acarbose (Precose®) and miglitol (Glyset®), work by interfering with the absorption of carbohydrates in the intestines. This results in lower blood glucose levels, though are not as effective as metformin or the sulfonylureas. They can be combined with other medications if the first medication does not lower blood glucose levels sufficiently.
The main side effects of alpha-glucosidase inhibitors are gas (flatulence), diarrhea, and abdominal pain; starting with a low dose may minimize these side effects. The medication is usually taken three times per day with the first bite of each meal.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
Canadian Diabetes Associates
(www.diabetes.ca)
U.S. Center for Disease Control and Prevention
(www.cdc.gov/diabetes)
[1-4]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Ismail, K, Winkley, K, Rabe-Hesketh, S. Systematic review and meta-analysis of randomised controlled trials of psychological interventions to improve glycaemic control in patients with type 2 diabetes. Lancet 2004; 363:1589.
2. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
3. Nathan, DM, Buse, JB, Davidson, MB, et al. Management of hyperglycemia in type 2 diabetes: a consensus algorithm for the initiation and adjustment of therapy: a consensus statement from the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care 2006; 29:1963.
4. Norris, SL, Zhang, X, Avenell, A, et al. Long-term effectiveness of lifestyle and behavioral weight loss interventions in adults with type 2 diabetes: a meta-analysis. Am J Med 2004; 117:762.
Tuesday, October 16, 2007
Diabetes type 2: Insulin treatment
INTRODUCTION — Type 2 diabetes mellitus occurs when the pancreas (an organ in the abdomen) produces insufficient amounts of the hormone insulin and/or the body's tissues become resistant to normal or even high levels of insulin. This causes high blood glucose (sugar) levels, which can lead to a number of complications if untreated.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain normal or near-normal blood glucose levels. Treatment includes lifestyle adjustments, self-care measures, and medications, which can minimize the risk of diabetes-related and cardiovascular complications (eg, heart attacks and strokes). Learning to manage diabetes is a process that continues over a lifetime. The diagnosis of diabetes can be overwhelming at the beginning; however, most people are able to lead normal lives and many patients become experts in their own care.
This topic review discusses the role of insulin in blood glucose control for patients with type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient information: Diabetes mellitus; type 2" and see "Patient information: Self-blood glucose monitoring" and see "Patient information: Hypoglycemia (low blood glucose) in diabetes" and see "Patient information: Lifestyle modifications in type 2 diabetes" and see "Patient information: Preventing complications in diabetes mellitus").
IMPORTANCE OF BLOOD GLUCOSE CONTROL — Keeping blood glucose levels in control is one way to decrease the risk of complications related to type 2 diabetes. The most common complication of type 2 diabetes is heart disease, also known as macrovascular disease. Macro- means large, and vascular means vessels. Untreated heart disease increases the risk of heart attack.
Individuals with type 2 diabetes are also at increased risk of developing microvascular (small vessel) disease of the eyes, kidneys, and nerves, which can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. Microvascular and macrovascular complications usually occur after many years of diabetes and are related to elevated levels of blood glucose over time. However, these complications may be present when type 2 diabetes is first diagnosed due to a delay in seeking medical care.
One of the largest studies to examine the benefit of tight blood glucose control was the United Kingdom Prospective Diabetes Study (UKPDS). It demonstrated that strict glycemic control in patients with type 2 diabetes reduces the risk of microvascular disease. It is not clear if blood glucose control affects the risk of macrovascular complications [1]. However, other therapies are available to decrease these risks. (See "Patient information: Preventing complications in diabetes mellitus").
Monitoring — Most people with type 2 diabetes need to monitor their blood glucose levels at home. This is especially true if the person uses a medication for diabetes that can cause low blood glucose levels (eg, insulin).
Blood glucose control is often measured by checking the blood glucose level before the first meal of the day (fasting). A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), although some people will have a different goal. A healthcare provider can help to determine this goal with the patient. Some people will need to test their blood glucose level before and/or after other meals during the day. The frequency of testing and blood glucose goals can change over time, so periodic visits to discuss these issues are important. (See "Patient information: Self-blood glucose monitoring").
Blood glucose control can also be measured with a blood test called A1C. The A1C blood test measures the average blood glucose level during the past two to three months. The test is done by giving a small sample of blood from a vein or fingertip in a clinician's office. The goal A1C for most people with type 2 diabetes is less than 7 percent, which corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show table 1). A healthcare provider can determine a person's individual A1C goal.
The average blood glucose goal (150 mg/dl or 8.3 mmol/L) is higher than the fasting blood glucose goal (100 mg/dL or 5.6 mmol/L) for several reasons. Blood glucose levels increase after eating. The amount and speed of the increase depend upon the type and amount of food eaten at a particular meal. The increase also depends upon the type and dose of diabetes treatment(s) used and the person's activity level.
How often to see your clinician — Most patients with type 2 diabetes meet with their healthcare provider every three to four months; blood glucose levels and medications, including insulin dosing, are reviewed at these visits, helping patients to fine-tune their diabetes control.
TREATMENT OPTIONS — Most people who are newly diagnosed with type 2 diabetes are usually treated with a combination of diet, exercise, and an oral medication (eg, pills). Some oral medications (eg, metformin) improve the body's response to insulin. Other medications cause the body to produce more insulin. (See "Patient information: Diabetes type 2: Treatment").
A second medication may be added within the first two to three months if blood glucose control is not adequate. "Adequate" control is defined as an A1C level less than 7 percent for most people; insulin may be recommended early if the A1C remains elevated despite lifestyle changes and diabetes pills, especially if the A1C is higher than 8.5 percent.
The need for a second medication is not uncommon [2]. Type 2 diabetes typically progresses with age, causing the body to produce less insulin and resist the action of insulin that is produced. In addition, it can be difficult for some people to follow the recommended diet, exercise, or treatment plan. Being diagnosed with a new medical problem or requiring a new medication can also change the body's needs for insulin, sometimes requiring a change in diabetes treatment. For example, when a person with type 2 diabetes takes corticosteroids (eg, prednisone) for an asthma attack, the blood glucose levels increase. This usually requires a higher dose of diabetes medication.
Oral medication plus insulin — Some people with type 2 diabetes require only oral medications for treatment. Other people will need to add insulin because their blood glucose levels are not controlled. Using a combination of treatments (oral medication plus insulin) generally means that the patient can take a lower dose of insulin, compared to if insulin treatment is used alone. There may also be a reduced risk of weight gain if combination therapy is used.
Insulin is usually given once per day, either in the morning or at bedtime. Small insulin doses are generally recommended when treatment first begins; the dose is adjusted over days, weeks, and months, once the body's response to insulin treatment is known.
To determine how and when to adjust the dose, the blood glucose level should be measured every morning before eating. If the value is consistently higher than 130 mg/dL (7.2 mmol/L), the clinician may recommend increasing the insulin dose. (See "Patient information: Self-blood glucose monitoring").
Insulin alone — Current recommendations are for most people with type 2 diabetes to be treated with metformin plus another medication such as insulin, as necessary. However, for a variety of reasons, some people are treated only with insulin. People taking insulin alone often require two injections of intermediate-acting insulin or one injection of long-acting insulin per day (see "Types of insulin" below). (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
If a long-acting insulin or a twice daily injection of intermediate-acting insulin is not adequate to control blood glucose levels, a more intensive insulin treatment regimen may be recommended. Intensive insulin treatment requires at least two injections of insulin per day, usually including a rapid-acting and long-acting insulin, or the use of an insulin pump. It also requires that the person monitor their blood glucose levels several times per day. This is discussed in greater detail in a separate topic review. (See "Patient information: Diabetes type 1: Insulin treatment", section on intensive insulin treatment).
TYPES OF INSULIN — There are several types of insulin. These types are classified according to how quickly the insulin begins to work and how long it remains active (show table 2):
Injectable insulin Rapid-acting (eg, insulin lispro [Humalog®], insulin aspart [Novolog®], and insulin glulisine [Apidra®]) Short-acting (eg, insulin regular) Intermediate-acting (eg, insulin NPH) Long-acting (eg, insulin glargine [Lantus®], insulin detemir [Levemir®])
The various types of insulin can be used in combination to achieve around-the-clock blood glucose control.
Inhaled insulin — An inhaled form of rapid-acting insulin is available, although it is not yet in common use. Inhaled insulin may be used in combination with long-acting insulin injections. The main issue with this new treatment is that it is difficult to make adjustments in the dose. Patients interested in using this type of insulin should talk with their health care provider.
INSULIN ADMINISTRATION — Insulin cannot be taken in pill form. It is usually injected into the layer of fat under the skin (called subcutaneous injection).
The following figure demonstrates the sites where insulin may be injected (show figure 1). Patients as well as parents or partners should learn to draw up and inject insulin. The site also determines how quickly the insulin is absorbed. (See "Site of injection" below).
Drawing up insulin — There are many different types of syringes and needles, so it's best to get specific instructions for drawing up insulin from a healthcare provider. Basic information is provided in the table (show table 2). Persons using an insulin pen should follow the instructions provided by the pen manufacturer and their clinician (see "Insulin pen injectors" below).
Before drawing up insulin, it is important to know the dose and type of insulin needed; persons using more than one type of insulin should calculate the total dose needed before drawing up their insulin. Some persons, including children and those with difficulty seeing, may need assistance. Magnification and other assistive devices are available. People who have difficulty drawing up their insulin should discuss this with their clinician.
Injection angle — Insulin is usually injected under the skin using a needle and syringe (show figure 2). It is important to use the correct injection angle since injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. On the other hand, injections that are too shallow are more painful and not absorbed well.
The best angle for insulin injection depends upon a patient's body type, injection site, and length of the needle used. A healthcare professional can help determine the right angle of injection.
Injection technique — The following is a description of subcutaneous insulin injection. Choose the site to inject (show figure 1). It is not necessary to clean the skin with alcohol unless the skin is dirty. Pinch up a fold of skin and quickly insert the needle at a 90º angle (or other angle, as described above, show figure 2). Keep the skin pinched to avoid injecting insulin into the muscle. Push the plunger down completely to inject the insulin. Hold the syringe and needle in place for five seconds. Release the skin fold. Remove the needle from the skin.
If blood or clear fluid (insulin) is seen at the injection site, the patient should apply pressure to the area for five to eight seconds. The area should not be rubbed because this can cause the insulin to be absorbed too quickly.
Needles and syringes should be used once and then thrown away; needles become dull quickly, potentially increasing the pain of injection. Used needles and syringes should not be included with regular household trash, but should instead be placed in a puncture-proof container (also known as a sharps container), available from most pharmacies or hospital supply stores.
Some patients wonder about the safety of injecting insulin through their clothing. One small study examined the risks and benefits of this technique, and found that blood glucose control did not differ between the group that injected insulin through a single layer of clothing and those that injected directly into the skin [3]. There were no reports of infections in either group, although a few patients who injected through clothing reported blood stains on their clothing or bruises on the skin. People who are interested in using this technique should speak with their healthcare provider before trying it.
Insulin pen injectors — Insulin pen injectors are available and may be more convenient to carry and use when away from home. Most are approximately the size of a large writing pen and contain a disposable insulin cartridge and needle. Some types of insulin and some insulin mixtures are not available in cartridges, meaning pens may not be an option in some situations.
Pens are especially useful for accurately injecting very small doses of insulin, and may be helpful for persons with impaired vision. Pens are generally more expensive than traditional syringes and needles. A number of insulin pens are available, and the specific instructions for use of each type should be obtained from the manufacturer or a healthcare provider.
OTHER FACTORS AFFECTING INSULIN ACTION — Several factors can affect how injected insulin works.
Dose of insulin injected — The dose of insulin injected affects the rate at which the body absorbs it. Larger doses of insulin may be absorbed more slowly than smaller doses.
Site of injection — Clinicians usually recommend rotating injection sites to minimize tissue irritation. When changing sites, it is important to keep in mind that insulin is absorbed at different rates in different areas of the body.
Insulin is absorbed fastest from the abdominal area, slowest from the leg and buttock, and at an intermediate rate from the arm. This may vary with the amount of fat present; areas with more fat under the skin absorb insulin more slowly (show figure 1).
It is reasonable to use the same general area for injections given at the same time of the day. Sometimes abdominal injections, which are absorbed more quickly, are preferred before meals. Injection into the thigh or buttock may be best for the evening dose because the insulin will be absorbed more slowly during the night.
Smoking and physical activity — Any factors that alter the rate of blood flow through the skin and fat will change insulin absorption. Smoking decreases blood flow. In contrast, factors that increase blood flow (such as exercise, saunas, hot baths, and massage of the injection site) increase insulin absorption. To avoid low blood sugar, insulin injections should be given after a bath or sauna. It is best to inject insulin into the arm or abdomen and wait 30 minutes before running. A lower dose of insulin may be recommended before or after exercise; this should be discussed with a healthcare provider.
Time since opening the bottle — Most insulin remains potent and effective for up to a month after the bottle has been opened (if kept in the refrigerator between injections). However, the potency of intermediate and long acting insulin begins to decrease after 30 days. This can be a problem for people who require very small doses of insulin, for whom a bottle might last two months or more. It is advisable to start a new bottle at least every 30 days.
For very rapid acting insulin used in pen injectors, it is acceptable to keep the pen injector at room temperature (in a purse or jacket pocket) for up to 14 days, provided that the pen is not exposed to temperature extremes. However, after 14 days, a new insulin cartridge or pen should be used, even if there is insulin left in the old cartridge.
Individual differences — The same dose of the same type of insulin may have different effects in different people with diabetes. Some trial and error is usually necessary to find the ideal type(s) and dose of insulin and schedule for each person.
Insulin needs often change over a person's lifetime. Changes in weight, diet, health conditions (including pregnancy), activity level, and occupation can have an impact on the amount of insulin needed to control blood glucose levels. Patients are often able to adjust their own insulin dose, but may require assistance in some situations. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
SPECIAL SITUATIONS — Several special situations can complicate insulin treatment for a person with diabetes. With advance planning and careful calculation, these situations are less likely to cause serious difficulties. A healthcare provider can assist patients in handling these situations.
Eating out — Eating out can be challenging since ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. Patients can estimate their insulin needs in several ways, including nutrition information from restaurants or a hand-held reference book.
Hypo- and hyperglycemia can occur more easily in situations where new or different foods are eaten; thus patients should keep a fast-acting source of carbohydrates and blood glucose monitor on hand at all times. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Surgery — Patients who undergo surgery may be instructed not to eat for eight to 12 hours before their procedure. A healthcare provider can help to determine the dose and timing of insulin before and after the procedure, especially if a patient will be unable to eat a normal diet afterwards.
Infections — Mild infections, such as a cold, sore throat, or urinary tract infection, can cause blood glucose levels to rise. In this situation, frequent telephone contact with a healthcare provider, careful blood glucose monitoring, and increasing the insulin dose are often recommended. It is important to drink an adequate amount of fluids while ill to avoid dehydration. Patients with nausea or vomiting may require medication to control their symptoms and avoid dehydration.
Travel — Managing blood glucose levels and insulin treatment while traveling can be difficult, especially when traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making careful blood glucose monitoring essential. Patients should speak with their healthcare provider before traveling to develop a treatment plan. (See "Patient information: General travel advice", section on Traveling with medical conditions).
STAYING MOTIVATED — Living with diabetes can be very demanding and some patients lose motivation over time. Healthcare providers can provide tips and encouragement to help patients stay on track. Helpful information and support is also available from the American Diabetes Association (ADA), at (800)-DIABETES (800-342-2383) and at www.diabetes.org.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
Canadian Diabetes Associates
(www.diabetes.ca)
Juvenile Diabetes Research Foundation
(www.jdrf.org)
U.S. Center for Disease Control and Prevention
(www.cdc.gov/diabetes)
[1-5]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
2. Turner, RC, Cull, CA, Frighi, V, Holman, RR for the UK Prospective Diabetes Study (UKPDS) Group. Glycemic control with diet, sulfonylurea, metformin, or insulin in patients with type 2 diabetes. Progressive requirement for multiple therapies (UKPDS 49). JAMA 1999; 281:2005.
3. Fleming, DR, Jacober, SJ, Vandenberg, MA, et al. The safety of injecting insulin through clothing. Diabetes Care 1997; 20:244.
4. Yki-Järvinen, H, Dressler, A, Ziemen, M. Less nocturnal hypoglycemia and better post-dinner glucose control with bedtime insulin glargine compared with bedtime NPH insulin during insulin combination therapy in type 2 diabetes. Diabetes Care 2000; 23:1130.
5. Taylor, R, Davies, R, Fox, C, et al. Appropriate insulin regimes for type 2 diabetes: a multicenter randomized crossover study. Diabetes Care 2000; 23:1612.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain normal or near-normal blood glucose levels. Treatment includes lifestyle adjustments, self-care measures, and medications, which can minimize the risk of diabetes-related and cardiovascular complications (eg, heart attacks and strokes). Learning to manage diabetes is a process that continues over a lifetime. The diagnosis of diabetes can be overwhelming at the beginning; however, most people are able to lead normal lives and many patients become experts in their own care.
This topic review discusses the role of insulin in blood glucose control for patients with type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient information: Diabetes mellitus; type 2" and see "Patient information: Self-blood glucose monitoring" and see "Patient information: Hypoglycemia (low blood glucose) in diabetes" and see "Patient information: Lifestyle modifications in type 2 diabetes" and see "Patient information: Preventing complications in diabetes mellitus").
IMPORTANCE OF BLOOD GLUCOSE CONTROL — Keeping blood glucose levels in control is one way to decrease the risk of complications related to type 2 diabetes. The most common complication of type 2 diabetes is heart disease, also known as macrovascular disease. Macro- means large, and vascular means vessels. Untreated heart disease increases the risk of heart attack.
Individuals with type 2 diabetes are also at increased risk of developing microvascular (small vessel) disease of the eyes, kidneys, and nerves, which can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. Microvascular and macrovascular complications usually occur after many years of diabetes and are related to elevated levels of blood glucose over time. However, these complications may be present when type 2 diabetes is first diagnosed due to a delay in seeking medical care.
One of the largest studies to examine the benefit of tight blood glucose control was the United Kingdom Prospective Diabetes Study (UKPDS). It demonstrated that strict glycemic control in patients with type 2 diabetes reduces the risk of microvascular disease. It is not clear if blood glucose control affects the risk of macrovascular complications [1]. However, other therapies are available to decrease these risks. (See "Patient information: Preventing complications in diabetes mellitus").
Monitoring — Most people with type 2 diabetes need to monitor their blood glucose levels at home. This is especially true if the person uses a medication for diabetes that can cause low blood glucose levels (eg, insulin).
Blood glucose control is often measured by checking the blood glucose level before the first meal of the day (fasting). A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), although some people will have a different goal. A healthcare provider can help to determine this goal with the patient. Some people will need to test their blood glucose level before and/or after other meals during the day. The frequency of testing and blood glucose goals can change over time, so periodic visits to discuss these issues are important. (See "Patient information: Self-blood glucose monitoring").
Blood glucose control can also be measured with a blood test called A1C. The A1C blood test measures the average blood glucose level during the past two to three months. The test is done by giving a small sample of blood from a vein or fingertip in a clinician's office. The goal A1C for most people with type 2 diabetes is less than 7 percent, which corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show table 1). A healthcare provider can determine a person's individual A1C goal.
The average blood glucose goal (150 mg/dl or 8.3 mmol/L) is higher than the fasting blood glucose goal (100 mg/dL or 5.6 mmol/L) for several reasons. Blood glucose levels increase after eating. The amount and speed of the increase depend upon the type and amount of food eaten at a particular meal. The increase also depends upon the type and dose of diabetes treatment(s) used and the person's activity level.
How often to see your clinician — Most patients with type 2 diabetes meet with their healthcare provider every three to four months; blood glucose levels and medications, including insulin dosing, are reviewed at these visits, helping patients to fine-tune their diabetes control.
TREATMENT OPTIONS — Most people who are newly diagnosed with type 2 diabetes are usually treated with a combination of diet, exercise, and an oral medication (eg, pills). Some oral medications (eg, metformin) improve the body's response to insulin. Other medications cause the body to produce more insulin. (See "Patient information: Diabetes type 2: Treatment").
A second medication may be added within the first two to three months if blood glucose control is not adequate. "Adequate" control is defined as an A1C level less than 7 percent for most people; insulin may be recommended early if the A1C remains elevated despite lifestyle changes and diabetes pills, especially if the A1C is higher than 8.5 percent.
The need for a second medication is not uncommon [2]. Type 2 diabetes typically progresses with age, causing the body to produce less insulin and resist the action of insulin that is produced. In addition, it can be difficult for some people to follow the recommended diet, exercise, or treatment plan. Being diagnosed with a new medical problem or requiring a new medication can also change the body's needs for insulin, sometimes requiring a change in diabetes treatment. For example, when a person with type 2 diabetes takes corticosteroids (eg, prednisone) for an asthma attack, the blood glucose levels increase. This usually requires a higher dose of diabetes medication.
Oral medication plus insulin — Some people with type 2 diabetes require only oral medications for treatment. Other people will need to add insulin because their blood glucose levels are not controlled. Using a combination of treatments (oral medication plus insulin) generally means that the patient can take a lower dose of insulin, compared to if insulin treatment is used alone. There may also be a reduced risk of weight gain if combination therapy is used.
Insulin is usually given once per day, either in the morning or at bedtime. Small insulin doses are generally recommended when treatment first begins; the dose is adjusted over days, weeks, and months, once the body's response to insulin treatment is known.
To determine how and when to adjust the dose, the blood glucose level should be measured every morning before eating. If the value is consistently higher than 130 mg/dL (7.2 mmol/L), the clinician may recommend increasing the insulin dose. (See "Patient information: Self-blood glucose monitoring").
Insulin alone — Current recommendations are for most people with type 2 diabetes to be treated with metformin plus another medication such as insulin, as necessary. However, for a variety of reasons, some people are treated only with insulin. People taking insulin alone often require two injections of intermediate-acting insulin or one injection of long-acting insulin per day (see "Types of insulin" below). (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
If a long-acting insulin or a twice daily injection of intermediate-acting insulin is not adequate to control blood glucose levels, a more intensive insulin treatment regimen may be recommended. Intensive insulin treatment requires at least two injections of insulin per day, usually including a rapid-acting and long-acting insulin, or the use of an insulin pump. It also requires that the person monitor their blood glucose levels several times per day. This is discussed in greater detail in a separate topic review. (See "Patient information: Diabetes type 1: Insulin treatment", section on intensive insulin treatment).
TYPES OF INSULIN — There are several types of insulin. These types are classified according to how quickly the insulin begins to work and how long it remains active (show table 2):
Injectable insulin Rapid-acting (eg, insulin lispro [Humalog®], insulin aspart [Novolog®], and insulin glulisine [Apidra®]) Short-acting (eg, insulin regular) Intermediate-acting (eg, insulin NPH) Long-acting (eg, insulin glargine [Lantus®], insulin detemir [Levemir®])
The various types of insulin can be used in combination to achieve around-the-clock blood glucose control.
Inhaled insulin — An inhaled form of rapid-acting insulin is available, although it is not yet in common use. Inhaled insulin may be used in combination with long-acting insulin injections. The main issue with this new treatment is that it is difficult to make adjustments in the dose. Patients interested in using this type of insulin should talk with their health care provider.
INSULIN ADMINISTRATION — Insulin cannot be taken in pill form. It is usually injected into the layer of fat under the skin (called subcutaneous injection).
The following figure demonstrates the sites where insulin may be injected (show figure 1). Patients as well as parents or partners should learn to draw up and inject insulin. The site also determines how quickly the insulin is absorbed. (See "Site of injection" below).
Drawing up insulin — There are many different types of syringes and needles, so it's best to get specific instructions for drawing up insulin from a healthcare provider. Basic information is provided in the table (show table 2). Persons using an insulin pen should follow the instructions provided by the pen manufacturer and their clinician (see "Insulin pen injectors" below).
Before drawing up insulin, it is important to know the dose and type of insulin needed; persons using more than one type of insulin should calculate the total dose needed before drawing up their insulin. Some persons, including children and those with difficulty seeing, may need assistance. Magnification and other assistive devices are available. People who have difficulty drawing up their insulin should discuss this with their clinician.
Injection angle — Insulin is usually injected under the skin using a needle and syringe (show figure 2). It is important to use the correct injection angle since injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. On the other hand, injections that are too shallow are more painful and not absorbed well.
The best angle for insulin injection depends upon a patient's body type, injection site, and length of the needle used. A healthcare professional can help determine the right angle of injection.
Injection technique — The following is a description of subcutaneous insulin injection. Choose the site to inject (show figure 1). It is not necessary to clean the skin with alcohol unless the skin is dirty. Pinch up a fold of skin and quickly insert the needle at a 90º angle (or other angle, as described above, show figure 2). Keep the skin pinched to avoid injecting insulin into the muscle. Push the plunger down completely to inject the insulin. Hold the syringe and needle in place for five seconds. Release the skin fold. Remove the needle from the skin.
If blood or clear fluid (insulin) is seen at the injection site, the patient should apply pressure to the area for five to eight seconds. The area should not be rubbed because this can cause the insulin to be absorbed too quickly.
Needles and syringes should be used once and then thrown away; needles become dull quickly, potentially increasing the pain of injection. Used needles and syringes should not be included with regular household trash, but should instead be placed in a puncture-proof container (also known as a sharps container), available from most pharmacies or hospital supply stores.
Some patients wonder about the safety of injecting insulin through their clothing. One small study examined the risks and benefits of this technique, and found that blood glucose control did not differ between the group that injected insulin through a single layer of clothing and those that injected directly into the skin [3]. There were no reports of infections in either group, although a few patients who injected through clothing reported blood stains on their clothing or bruises on the skin. People who are interested in using this technique should speak with their healthcare provider before trying it.
Insulin pen injectors — Insulin pen injectors are available and may be more convenient to carry and use when away from home. Most are approximately the size of a large writing pen and contain a disposable insulin cartridge and needle. Some types of insulin and some insulin mixtures are not available in cartridges, meaning pens may not be an option in some situations.
Pens are especially useful for accurately injecting very small doses of insulin, and may be helpful for persons with impaired vision. Pens are generally more expensive than traditional syringes and needles. A number of insulin pens are available, and the specific instructions for use of each type should be obtained from the manufacturer or a healthcare provider.
OTHER FACTORS AFFECTING INSULIN ACTION — Several factors can affect how injected insulin works.
Dose of insulin injected — The dose of insulin injected affects the rate at which the body absorbs it. Larger doses of insulin may be absorbed more slowly than smaller doses.
Site of injection — Clinicians usually recommend rotating injection sites to minimize tissue irritation. When changing sites, it is important to keep in mind that insulin is absorbed at different rates in different areas of the body.
Insulin is absorbed fastest from the abdominal area, slowest from the leg and buttock, and at an intermediate rate from the arm. This may vary with the amount of fat present; areas with more fat under the skin absorb insulin more slowly (show figure 1).
It is reasonable to use the same general area for injections given at the same time of the day. Sometimes abdominal injections, which are absorbed more quickly, are preferred before meals. Injection into the thigh or buttock may be best for the evening dose because the insulin will be absorbed more slowly during the night.
Smoking and physical activity — Any factors that alter the rate of blood flow through the skin and fat will change insulin absorption. Smoking decreases blood flow. In contrast, factors that increase blood flow (such as exercise, saunas, hot baths, and massage of the injection site) increase insulin absorption. To avoid low blood sugar, insulin injections should be given after a bath or sauna. It is best to inject insulin into the arm or abdomen and wait 30 minutes before running. A lower dose of insulin may be recommended before or after exercise; this should be discussed with a healthcare provider.
Time since opening the bottle — Most insulin remains potent and effective for up to a month after the bottle has been opened (if kept in the refrigerator between injections). However, the potency of intermediate and long acting insulin begins to decrease after 30 days. This can be a problem for people who require very small doses of insulin, for whom a bottle might last two months or more. It is advisable to start a new bottle at least every 30 days.
For very rapid acting insulin used in pen injectors, it is acceptable to keep the pen injector at room temperature (in a purse or jacket pocket) for up to 14 days, provided that the pen is not exposed to temperature extremes. However, after 14 days, a new insulin cartridge or pen should be used, even if there is insulin left in the old cartridge.
Individual differences — The same dose of the same type of insulin may have different effects in different people with diabetes. Some trial and error is usually necessary to find the ideal type(s) and dose of insulin and schedule for each person.
Insulin needs often change over a person's lifetime. Changes in weight, diet, health conditions (including pregnancy), activity level, and occupation can have an impact on the amount of insulin needed to control blood glucose levels. Patients are often able to adjust their own insulin dose, but may require assistance in some situations. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
SPECIAL SITUATIONS — Several special situations can complicate insulin treatment for a person with diabetes. With advance planning and careful calculation, these situations are less likely to cause serious difficulties. A healthcare provider can assist patients in handling these situations.
Eating out — Eating out can be challenging since ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. Patients can estimate their insulin needs in several ways, including nutrition information from restaurants or a hand-held reference book.
Hypo- and hyperglycemia can occur more easily in situations where new or different foods are eaten; thus patients should keep a fast-acting source of carbohydrates and blood glucose monitor on hand at all times. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Surgery — Patients who undergo surgery may be instructed not to eat for eight to 12 hours before their procedure. A healthcare provider can help to determine the dose and timing of insulin before and after the procedure, especially if a patient will be unable to eat a normal diet afterwards.
Infections — Mild infections, such as a cold, sore throat, or urinary tract infection, can cause blood glucose levels to rise. In this situation, frequent telephone contact with a healthcare provider, careful blood glucose monitoring, and increasing the insulin dose are often recommended. It is important to drink an adequate amount of fluids while ill to avoid dehydration. Patients with nausea or vomiting may require medication to control their symptoms and avoid dehydration.
Travel — Managing blood glucose levels and insulin treatment while traveling can be difficult, especially when traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making careful blood glucose monitoring essential. Patients should speak with their healthcare provider before traveling to develop a treatment plan. (See "Patient information: General travel advice", section on Traveling with medical conditions).
STAYING MOTIVATED — Living with diabetes can be very demanding and some patients lose motivation over time. Healthcare providers can provide tips and encouragement to help patients stay on track. Helpful information and support is also available from the American Diabetes Association (ADA), at (800)-DIABETES (800-342-2383) and at www.diabetes.org.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
Canadian Diabetes Associates
(www.diabetes.ca)
Juvenile Diabetes Research Foundation
(www.jdrf.org)
U.S. Center for Disease Control and Prevention
(www.cdc.gov/diabetes)
[1-5]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
2. Turner, RC, Cull, CA, Frighi, V, Holman, RR for the UK Prospective Diabetes Study (UKPDS) Group. Glycemic control with diet, sulfonylurea, metformin, or insulin in patients with type 2 diabetes. Progressive requirement for multiple therapies (UKPDS 49). JAMA 1999; 281:2005.
3. Fleming, DR, Jacober, SJ, Vandenberg, MA, et al. The safety of injecting insulin through clothing. Diabetes Care 1997; 20:244.
4. Yki-Järvinen, H, Dressler, A, Ziemen, M. Less nocturnal hypoglycemia and better post-dinner glucose control with bedtime insulin glargine compared with bedtime NPH insulin during insulin combination therapy in type 2 diabetes. Diabetes Care 2000; 23:1130.
5. Taylor, R, Davies, R, Fox, C, et al. Appropriate insulin regimes for type 2 diabetes: a multicenter randomized crossover study. Diabetes Care 2000; 23:1612.
Diabetes type 2: Insulin treatment
INTRODUCTION — Type 2 diabetes mellitus occurs when the pancreas (an organ in the abdomen) produces insufficient amounts of the hormone insulin and/or the body's tissues become resistant to normal or even high levels of insulin. This causes high blood glucose (sugar) levels, which can lead to a number of complications if untreated.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain normal or near-normal blood glucose levels. Treatment includes lifestyle adjustments, self-care measures, and medications, which can minimize the risk of diabetes-related and cardiovascular complications (eg, heart attacks and strokes). Learning to manage diabetes is a process that continues over a lifetime. The diagnosis of diabetes can be overwhelming at the beginning; however, most people are able to lead normal lives and many patients become experts in their own care.
This topic review discusses the role of insulin in blood glucose control for patients with type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient information: Diabetes mellitus; type 2" and see "Patient information: Self-blood glucose monitoring" and see "Patient information: Hypoglycemia (low blood glucose) in diabetes" and see "Patient information: Lifestyle modifications in type 2 diabetes" and see "Patient information: Preventing complications in diabetes mellitus").
IMPORTANCE OF BLOOD GLUCOSE CONTROL — Keeping blood glucose levels in control is one way to decrease the risk of complications related to type 2 diabetes. The most common complication of type 2 diabetes is heart disease, also known as macrovascular disease. Macro- means large, and vascular means vessels. Untreated heart disease increases the risk of heart attack.
Individuals with type 2 diabetes are also at increased risk of developing microvascular (small vessel) disease of the eyes, kidneys, and nerves, which can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. Microvascular and macrovascular complications usually occur after many years of diabetes and are related to elevated levels of blood glucose over time. However, these complications may be present when type 2 diabetes is first diagnosed due to a delay in seeking medical care.
One of the largest studies to examine the benefit of tight blood glucose control was the United Kingdom Prospective Diabetes Study (UKPDS). It demonstrated that strict glycemic control in patients with type 2 diabetes reduces the risk of microvascular disease. It is not clear if blood glucose control affects the risk of macrovascular complications [1]. However, other therapies are available to decrease these risks. (See "Patient information: Preventing complications in diabetes mellitus").
Monitoring — Most people with type 2 diabetes need to monitor their blood glucose levels at home. This is especially true if the person uses a medication for diabetes that can cause low blood glucose levels (eg, insulin).
Blood glucose control is often measured by checking the blood glucose level before the first meal of the day (fasting). A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), although some people will have a different goal. A healthcare provider can help to determine this goal with the patient. Some people will need to test their blood glucose level before and/or after other meals during the day. The frequency of testing and blood glucose goals can change over time, so periodic visits to discuss these issues are important. (See "Patient information: Self-blood glucose monitoring").
Blood glucose control can also be measured with a blood test called A1C. The A1C blood test measures the average blood glucose level during the past two to three months. The test is done by giving a small sample of blood from a vein or fingertip in a clinician's office. The goal A1C for most people with type 2 diabetes is less than 7 percent, which corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show table 1). A healthcare provider can determine a person's individual A1C goal.
The average blood glucose goal (150 mg/dl or 8.3 mmol/L) is higher than the fasting blood glucose goal (100 mg/dL or 5.6 mmol/L) for several reasons. Blood glucose levels increase after eating. The amount and speed of the increase depend upon the type and amount of food eaten at a particular meal. The increase also depends upon the type and dose of diabetes treatment(s) used and the person's activity level.
How often to see your clinician — Most patients with type 2 diabetes meet with their healthcare provider every three to four months; blood glucose levels and medications, including insulin dosing, are reviewed at these visits, helping patients to fine-tune their diabetes control.
TREATMENT OPTIONS — Most people who are newly diagnosed with type 2 diabetes are usually treated with a combination of diet, exercise, and an oral medication (eg, pills). Some oral medications (eg, metformin) improve the body's response to insulin. Other medications cause the body to produce more insulin. (See "Patient information: Diabetes type 2: Treatment").
A second medication may be added within the first two to three months if blood glucose control is not adequate. "Adequate" control is defined as an A1C level less than 7 percent for most people; insulin may be recommended early if the A1C remains elevated despite lifestyle changes and diabetes pills, especially if the A1C is higher than 8.5 percent.
The need for a second medication is not uncommon [2]. Type 2 diabetes typically progresses with age, causing the body to produce less insulin and resist the action of insulin that is produced. In addition, it can be difficult for some people to follow the recommended diet, exercise, or treatment plan. Being diagnosed with a new medical problem or requiring a new medication can also change the body's needs for insulin, sometimes requiring a change in diabetes treatment. For example, when a person with type 2 diabetes takes corticosteroids (eg, prednisone) for an asthma attack, the blood glucose levels increase. This usually requires a higher dose of diabetes medication.
Oral medication plus insulin — Some people with type 2 diabetes require only oral medications for treatment. Other people will need to add insulin because their blood glucose levels are not controlled. Using a combination of treatments (oral medication plus insulin) generally means that the patient can take a lower dose of insulin, compared to if insulin treatment is used alone. There may also be a reduced risk of weight gain if combination therapy is used.
Insulin is usually given once per day, either in the morning or at bedtime. Small insulin doses are generally recommended when treatment first begins; the dose is adjusted over days, weeks, and months, once the body's response to insulin treatment is known.
To determine how and when to adjust the dose, the blood glucose level should be measured every morning before eating. If the value is consistently higher than 130 mg/dL (7.2 mmol/L), the clinician may recommend increasing the insulin dose. (See "Patient information: Self-blood glucose monitoring").
Insulin alone — Current recommendations are for most people with type 2 diabetes to be treated with metformin plus another medication such as insulin, as necessary. However, for a variety of reasons, some people are treated only with insulin. People taking insulin alone often require two injections of intermediate-acting insulin or one injection of long-acting insulin per day (see "Types of insulin" below). (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
If a long-acting insulin or a twice daily injection of intermediate-acting insulin is not adequate to control blood glucose levels, a more intensive insulin treatment regimen may be recommended. Intensive insulin treatment requires at least two injections of insulin per day, usually including a rapid-acting and long-acting insulin, or the use of an insulin pump. It also requires that the person monitor their blood glucose levels several times per day. This is discussed in greater detail in a separate topic review. (See "Patient information: Diabetes type 1: Insulin treatment", section on intensive insulin treatment).
TYPES OF INSULIN — There are several types of insulin. These types are classified according to how quickly the insulin begins to work and how long it remains active (show table 2):
Injectable insulin Rapid-acting (eg, insulin lispro [Humalog®], insulin aspart [Novolog®], and insulin glulisine [Apidra®]) Short-acting (eg, insulin regular) Intermediate-acting (eg, insulin NPH) Long-acting (eg, insulin glargine [Lantus®], insulin detemir [Levemir®])
The various types of insulin can be used in combination to achieve around-the-clock blood glucose control.
Inhaled insulin — An inhaled form of rapid-acting insulin is available, although it is not yet in common use. Inhaled insulin may be used in combination with long-acting insulin injections. The main issue with this new treatment is that it is difficult to make adjustments in the dose. Patients interested in using this type of insulin should talk with their health care provider.
INSULIN ADMINISTRATION — Insulin cannot be taken in pill form. It is usually injected into the layer of fat under the skin (called subcutaneous injection).
The following figure demonstrates the sites where insulin may be injected (show figure 1). Patients as well as parents or partners should learn to draw up and inject insulin. The site also determines how quickly the insulin is absorbed. (See "Site of injection" below).
Drawing up insulin — There are many different types of syringes and needles, so it's best to get specific instructions for drawing up insulin from a healthcare provider. Basic information is provided in the table (show table 2). Persons using an insulin pen should follow the instructions provided by the pen manufacturer and their clinician (see "Insulin pen injectors" below).
Before drawing up insulin, it is important to know the dose and type of insulin needed; persons using more than one type of insulin should calculate the total dose needed before drawing up their insulin. Some persons, including children and those with difficulty seeing, may need assistance. Magnification and other assistive devices are available. People who have difficulty drawing up their insulin should discuss this with their clinician.
Injection angle — Insulin is usually injected under the skin using a needle and syringe (show figure 2). It is important to use the correct injection angle since injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. On the other hand, injections that are too shallow are more painful and not absorbed well.
The best angle for insulin injection depends upon a patient's body type, injection site, and length of the needle used. A healthcare professional can help determine the right angle of injection.
Injection technique — The following is a description of subcutaneous insulin injection. Choose the site to inject (show figure 1). It is not necessary to clean the skin with alcohol unless the skin is dirty. Pinch up a fold of skin and quickly insert the needle at a 90º angle (or other angle, as described above, show figure 2). Keep the skin pinched to avoid injecting insulin into the muscle. Push the plunger down completely to inject the insulin. Hold the syringe and needle in place for five seconds. Release the skin fold. Remove the needle from the skin.
If blood or clear fluid (insulin) is seen at the injection site, the patient should apply pressure to the area for five to eight seconds. The area should not be rubbed because this can cause the insulin to be absorbed too quickly.
Needles and syringes should be used once and then thrown away; needles become dull quickly, potentially increasing the pain of injection. Used needles and syringes should not be included with regular household trash, but should instead be placed in a puncture-proof container (also known as a sharps container), available from most pharmacies or hospital supply stores.
Some patients wonder about the safety of injecting insulin through their clothing. One small study examined the risks and benefits of this technique, and found that blood glucose control did not differ between the group that injected insulin through a single layer of clothing and those that injected directly into the skin [3]. There were no reports of infections in either group, although a few patients who injected through clothing reported blood stains on their clothing or bruises on the skin. People who are interested in using this technique should speak with their healthcare provider before trying it.
Insulin pen injectors — Insulin pen injectors are available and may be more convenient to carry and use when away from home. Most are approximately the size of a large writing pen and contain a disposable insulin cartridge and needle. Some types of insulin and some insulin mixtures are not available in cartridges, meaning pens may not be an option in some situations.
Pens are especially useful for accurately injecting very small doses of insulin, and may be helpful for persons with impaired vision. Pens are generally more expensive than traditional syringes and needles. A number of insulin pens are available, and the specific instructions for use of each type should be obtained from the manufacturer or a healthcare provider.
OTHER FACTORS AFFECTING INSULIN ACTION — Several factors can affect how injected insulin works.
Dose of insulin injected — The dose of insulin injected affects the rate at which the body absorbs it. Larger doses of insulin may be absorbed more slowly than smaller doses.
Site of injection — Clinicians usually recommend rotating injection sites to minimize tissue irritation. When changing sites, it is important to keep in mind that insulin is absorbed at different rates in different areas of the body.
Insulin is absorbed fastest from the abdominal area, slowest from the leg and buttock, and at an intermediate rate from the arm. This may vary with the amount of fat present; areas with more fat under the skin absorb insulin more slowly (show figure 1).
It is reasonable to use the same general area for injections given at the same time of the day. Sometimes abdominal injections, which are absorbed more quickly, are preferred before meals. Injection into the thigh or buttock may be best for the evening dose because the insulin will be absorbed more slowly during the night.
Smoking and physical activity — Any factors that alter the rate of blood flow through the skin and fat will change insulin absorption. Smoking decreases blood flow. In contrast, factors that increase blood flow (such as exercise, saunas, hot baths, and massage of the injection site) increase insulin absorption. To avoid low blood sugar, insulin injections should be given after a bath or sauna. It is best to inject insulin into the arm or abdomen and wait 30 minutes before running. A lower dose of insulin may be recommended before or after exercise; this should be discussed with a healthcare provider.
Time since opening the bottle — Most insulin remains potent and effective for up to a month after the bottle has been opened (if kept in the refrigerator between injections). However, the potency of intermediate and long acting insulin begins to decrease after 30 days. This can be a problem for people who require very small doses of insulin, for whom a bottle might last two months or more. It is advisable to start a new bottle at least every 30 days.
For very rapid acting insulin used in pen injectors, it is acceptable to keep the pen injector at room temperature (in a purse or jacket pocket) for up to 14 days, provided that the pen is not exposed to temperature extremes. However, after 14 days, a new insulin cartridge or pen should be used, even if there is insulin left in the old cartridge.
Individual differences — The same dose of the same type of insulin may have different effects in different people with diabetes. Some trial and error is usually necessary to find the ideal type(s) and dose of insulin and schedule for each person.
Insulin needs often change over a person's lifetime. Changes in weight, diet, health conditions (including pregnancy), activity level, and occupation can have an impact on the amount of insulin needed to control blood glucose levels. Patients are often able to adjust their own insulin dose, but may require assistance in some situations. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
SPECIAL SITUATIONS — Several special situations can complicate insulin treatment for a person with diabetes. With advance planning and careful calculation, these situations are less likely to cause serious difficulties. A healthcare provider can assist patients in handling these situations.
Eating out — Eating out can be challenging since ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. Patients can estimate their insulin needs in several ways, including nutrition information from restaurants or a hand-held reference book.
Hypo- and hyperglycemia can occur more easily in situations where new or different foods are eaten; thus patients should keep a fast-acting source of carbohydrates and blood glucose monitor on hand at all times. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Surgery — Patients who undergo surgery may be instructed not to eat for eight to 12 hours before their procedure. A healthcare provider can help to determine the dose and timing of insulin before and after the procedure, especially if a patient will be unable to eat a normal diet afterwards.
Infections — Mild infections, such as a cold, sore throat, or urinary tract infection, can cause blood glucose levels to rise. In this situation, frequent telephone contact with a healthcare provider, careful blood glucose monitoring, and increasing the insulin dose are often recommended. It is important to drink an adequate amount of fluids while ill to avoid dehydration. Patients with nausea or vomiting may require medication to control their symptoms and avoid dehydration.
Travel — Managing blood glucose levels and insulin treatment while traveling can be difficult, especially when traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making careful blood glucose monitoring essential. Patients should speak with their healthcare provider before traveling to develop a treatment plan. (See "Patient information: General travel advice", section on Traveling with medical conditions).
STAYING MOTIVATED — Living with diabetes can be very demanding and some patients lose motivation over time. Healthcare providers can provide tips and encouragement to help patients stay on track. Helpful information and support is also available from the American Diabetes Association (ADA), at (800)-DIABETES (800-342-2383) and at www.diabetes.org.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
Canadian Diabetes Associates
(www.diabetes.ca)
Juvenile Diabetes Research Foundation
(www.jdrf.org)
U.S. Center for Disease Control and Prevention
(www.cdc.gov/diabetes)
[1-5]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
2. Turner, RC, Cull, CA, Frighi, V, Holman, RR for the UK Prospective Diabetes Study (UKPDS) Group. Glycemic control with diet, sulfonylurea, metformin, or insulin in patients with type 2 diabetes. Progressive requirement for multiple therapies (UKPDS 49). JAMA 1999; 281:2005.
3. Fleming, DR, Jacober, SJ, Vandenberg, MA, et al. The safety of injecting insulin through clothing. Diabetes Care 1997; 20:244.
4. Yki-Järvinen, H, Dressler, A, Ziemen, M. Less nocturnal hypoglycemia and better post-dinner glucose control with bedtime insulin glargine compared with bedtime NPH insulin during insulin combination therapy in type 2 diabetes. Diabetes Care 2000; 23:1130.
5. Taylor, R, Davies, R, Fox, C, et al. Appropriate insulin regimes for type 2 diabetes: a multicenter randomized crossover study. Diabetes Care 2000; 23:1612.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain normal or near-normal blood glucose levels. Treatment includes lifestyle adjustments, self-care measures, and medications, which can minimize the risk of diabetes-related and cardiovascular complications (eg, heart attacks and strokes). Learning to manage diabetes is a process that continues over a lifetime. The diagnosis of diabetes can be overwhelming at the beginning; however, most people are able to lead normal lives and many patients become experts in their own care.
This topic review discusses the role of insulin in blood glucose control for patients with type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient information: Diabetes mellitus; type 2" and see "Patient information: Self-blood glucose monitoring" and see "Patient information: Hypoglycemia (low blood glucose) in diabetes" and see "Patient information: Lifestyle modifications in type 2 diabetes" and see "Patient information: Preventing complications in diabetes mellitus").
IMPORTANCE OF BLOOD GLUCOSE CONTROL — Keeping blood glucose levels in control is one way to decrease the risk of complications related to type 2 diabetes. The most common complication of type 2 diabetes is heart disease, also known as macrovascular disease. Macro- means large, and vascular means vessels. Untreated heart disease increases the risk of heart attack.
Individuals with type 2 diabetes are also at increased risk of developing microvascular (small vessel) disease of the eyes, kidneys, and nerves, which can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. Microvascular and macrovascular complications usually occur after many years of diabetes and are related to elevated levels of blood glucose over time. However, these complications may be present when type 2 diabetes is first diagnosed due to a delay in seeking medical care.
One of the largest studies to examine the benefit of tight blood glucose control was the United Kingdom Prospective Diabetes Study (UKPDS). It demonstrated that strict glycemic control in patients with type 2 diabetes reduces the risk of microvascular disease. It is not clear if blood glucose control affects the risk of macrovascular complications [1]. However, other therapies are available to decrease these risks. (See "Patient information: Preventing complications in diabetes mellitus").
Monitoring — Most people with type 2 diabetes need to monitor their blood glucose levels at home. This is especially true if the person uses a medication for diabetes that can cause low blood glucose levels (eg, insulin).
Blood glucose control is often measured by checking the blood glucose level before the first meal of the day (fasting). A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), although some people will have a different goal. A healthcare provider can help to determine this goal with the patient. Some people will need to test their blood glucose level before and/or after other meals during the day. The frequency of testing and blood glucose goals can change over time, so periodic visits to discuss these issues are important. (See "Patient information: Self-blood glucose monitoring").
Blood glucose control can also be measured with a blood test called A1C. The A1C blood test measures the average blood glucose level during the past two to three months. The test is done by giving a small sample of blood from a vein or fingertip in a clinician's office. The goal A1C for most people with type 2 diabetes is less than 7 percent, which corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show table 1). A healthcare provider can determine a person's individual A1C goal.
The average blood glucose goal (150 mg/dl or 8.3 mmol/L) is higher than the fasting blood glucose goal (100 mg/dL or 5.6 mmol/L) for several reasons. Blood glucose levels increase after eating. The amount and speed of the increase depend upon the type and amount of food eaten at a particular meal. The increase also depends upon the type and dose of diabetes treatment(s) used and the person's activity level.
How often to see your clinician — Most patients with type 2 diabetes meet with their healthcare provider every three to four months; blood glucose levels and medications, including insulin dosing, are reviewed at these visits, helping patients to fine-tune their diabetes control.
TREATMENT OPTIONS — Most people who are newly diagnosed with type 2 diabetes are usually treated with a combination of diet, exercise, and an oral medication (eg, pills). Some oral medications (eg, metformin) improve the body's response to insulin. Other medications cause the body to produce more insulin. (See "Patient information: Diabetes type 2: Treatment").
A second medication may be added within the first two to three months if blood glucose control is not adequate. "Adequate" control is defined as an A1C level less than 7 percent for most people; insulin may be recommended early if the A1C remains elevated despite lifestyle changes and diabetes pills, especially if the A1C is higher than 8.5 percent.
The need for a second medication is not uncommon [2]. Type 2 diabetes typically progresses with age, causing the body to produce less insulin and resist the action of insulin that is produced. In addition, it can be difficult for some people to follow the recommended diet, exercise, or treatment plan. Being diagnosed with a new medical problem or requiring a new medication can also change the body's needs for insulin, sometimes requiring a change in diabetes treatment. For example, when a person with type 2 diabetes takes corticosteroids (eg, prednisone) for an asthma attack, the blood glucose levels increase. This usually requires a higher dose of diabetes medication.
Oral medication plus insulin — Some people with type 2 diabetes require only oral medications for treatment. Other people will need to add insulin because their blood glucose levels are not controlled. Using a combination of treatments (oral medication plus insulin) generally means that the patient can take a lower dose of insulin, compared to if insulin treatment is used alone. There may also be a reduced risk of weight gain if combination therapy is used.
Insulin is usually given once per day, either in the morning or at bedtime. Small insulin doses are generally recommended when treatment first begins; the dose is adjusted over days, weeks, and months, once the body's response to insulin treatment is known.
To determine how and when to adjust the dose, the blood glucose level should be measured every morning before eating. If the value is consistently higher than 130 mg/dL (7.2 mmol/L), the clinician may recommend increasing the insulin dose. (See "Patient information: Self-blood glucose monitoring").
Insulin alone — Current recommendations are for most people with type 2 diabetes to be treated with metformin plus another medication such as insulin, as necessary. However, for a variety of reasons, some people are treated only with insulin. People taking insulin alone often require two injections of intermediate-acting insulin or one injection of long-acting insulin per day (see "Types of insulin" below). (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
If a long-acting insulin or a twice daily injection of intermediate-acting insulin is not adequate to control blood glucose levels, a more intensive insulin treatment regimen may be recommended. Intensive insulin treatment requires at least two injections of insulin per day, usually including a rapid-acting and long-acting insulin, or the use of an insulin pump. It also requires that the person monitor their blood glucose levels several times per day. This is discussed in greater detail in a separate topic review. (See "Patient information: Diabetes type 1: Insulin treatment", section on intensive insulin treatment).
TYPES OF INSULIN — There are several types of insulin. These types are classified according to how quickly the insulin begins to work and how long it remains active (show table 2):
Injectable insulin Rapid-acting (eg, insulin lispro [Humalog®], insulin aspart [Novolog®], and insulin glulisine [Apidra®]) Short-acting (eg, insulin regular) Intermediate-acting (eg, insulin NPH) Long-acting (eg, insulin glargine [Lantus®], insulin detemir [Levemir®])
The various types of insulin can be used in combination to achieve around-the-clock blood glucose control.
Inhaled insulin — An inhaled form of rapid-acting insulin is available, although it is not yet in common use. Inhaled insulin may be used in combination with long-acting insulin injections. The main issue with this new treatment is that it is difficult to make adjustments in the dose. Patients interested in using this type of insulin should talk with their health care provider.
INSULIN ADMINISTRATION — Insulin cannot be taken in pill form. It is usually injected into the layer of fat under the skin (called subcutaneous injection).
The following figure demonstrates the sites where insulin may be injected (show figure 1). Patients as well as parents or partners should learn to draw up and inject insulin. The site also determines how quickly the insulin is absorbed. (See "Site of injection" below).
Drawing up insulin — There are many different types of syringes and needles, so it's best to get specific instructions for drawing up insulin from a healthcare provider. Basic information is provided in the table (show table 2). Persons using an insulin pen should follow the instructions provided by the pen manufacturer and their clinician (see "Insulin pen injectors" below).
Before drawing up insulin, it is important to know the dose and type of insulin needed; persons using more than one type of insulin should calculate the total dose needed before drawing up their insulin. Some persons, including children and those with difficulty seeing, may need assistance. Magnification and other assistive devices are available. People who have difficulty drawing up their insulin should discuss this with their clinician.
Injection angle — Insulin is usually injected under the skin using a needle and syringe (show figure 2). It is important to use the correct injection angle since injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. On the other hand, injections that are too shallow are more painful and not absorbed well.
The best angle for insulin injection depends upon a patient's body type, injection site, and length of the needle used. A healthcare professional can help determine the right angle of injection.
Injection technique — The following is a description of subcutaneous insulin injection. Choose the site to inject (show figure 1). It is not necessary to clean the skin with alcohol unless the skin is dirty. Pinch up a fold of skin and quickly insert the needle at a 90º angle (or other angle, as described above, show figure 2). Keep the skin pinched to avoid injecting insulin into the muscle. Push the plunger down completely to inject the insulin. Hold the syringe and needle in place for five seconds. Release the skin fold. Remove the needle from the skin.
If blood or clear fluid (insulin) is seen at the injection site, the patient should apply pressure to the area for five to eight seconds. The area should not be rubbed because this can cause the insulin to be absorbed too quickly.
Needles and syringes should be used once and then thrown away; needles become dull quickly, potentially increasing the pain of injection. Used needles and syringes should not be included with regular household trash, but should instead be placed in a puncture-proof container (also known as a sharps container), available from most pharmacies or hospital supply stores.
Some patients wonder about the safety of injecting insulin through their clothing. One small study examined the risks and benefits of this technique, and found that blood glucose control did not differ between the group that injected insulin through a single layer of clothing and those that injected directly into the skin [3]. There were no reports of infections in either group, although a few patients who injected through clothing reported blood stains on their clothing or bruises on the skin. People who are interested in using this technique should speak with their healthcare provider before trying it.
Insulin pen injectors — Insulin pen injectors are available and may be more convenient to carry and use when away from home. Most are approximately the size of a large writing pen and contain a disposable insulin cartridge and needle. Some types of insulin and some insulin mixtures are not available in cartridges, meaning pens may not be an option in some situations.
Pens are especially useful for accurately injecting very small doses of insulin, and may be helpful for persons with impaired vision. Pens are generally more expensive than traditional syringes and needles. A number of insulin pens are available, and the specific instructions for use of each type should be obtained from the manufacturer or a healthcare provider.
OTHER FACTORS AFFECTING INSULIN ACTION — Several factors can affect how injected insulin works.
Dose of insulin injected — The dose of insulin injected affects the rate at which the body absorbs it. Larger doses of insulin may be absorbed more slowly than smaller doses.
Site of injection — Clinicians usually recommend rotating injection sites to minimize tissue irritation. When changing sites, it is important to keep in mind that insulin is absorbed at different rates in different areas of the body.
Insulin is absorbed fastest from the abdominal area, slowest from the leg and buttock, and at an intermediate rate from the arm. This may vary with the amount of fat present; areas with more fat under the skin absorb insulin more slowly (show figure 1).
It is reasonable to use the same general area for injections given at the same time of the day. Sometimes abdominal injections, which are absorbed more quickly, are preferred before meals. Injection into the thigh or buttock may be best for the evening dose because the insulin will be absorbed more slowly during the night.
Smoking and physical activity — Any factors that alter the rate of blood flow through the skin and fat will change insulin absorption. Smoking decreases blood flow. In contrast, factors that increase blood flow (such as exercise, saunas, hot baths, and massage of the injection site) increase insulin absorption. To avoid low blood sugar, insulin injections should be given after a bath or sauna. It is best to inject insulin into the arm or abdomen and wait 30 minutes before running. A lower dose of insulin may be recommended before or after exercise; this should be discussed with a healthcare provider.
Time since opening the bottle — Most insulin remains potent and effective for up to a month after the bottle has been opened (if kept in the refrigerator between injections). However, the potency of intermediate and long acting insulin begins to decrease after 30 days. This can be a problem for people who require very small doses of insulin, for whom a bottle might last two months or more. It is advisable to start a new bottle at least every 30 days.
For very rapid acting insulin used in pen injectors, it is acceptable to keep the pen injector at room temperature (in a purse or jacket pocket) for up to 14 days, provided that the pen is not exposed to temperature extremes. However, after 14 days, a new insulin cartridge or pen should be used, even if there is insulin left in the old cartridge.
Individual differences — The same dose of the same type of insulin may have different effects in different people with diabetes. Some trial and error is usually necessary to find the ideal type(s) and dose of insulin and schedule for each person.
Insulin needs often change over a person's lifetime. Changes in weight, diet, health conditions (including pregnancy), activity level, and occupation can have an impact on the amount of insulin needed to control blood glucose levels. Patients are often able to adjust their own insulin dose, but may require assistance in some situations. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
SPECIAL SITUATIONS — Several special situations can complicate insulin treatment for a person with diabetes. With advance planning and careful calculation, these situations are less likely to cause serious difficulties. A healthcare provider can assist patients in handling these situations.
Eating out — Eating out can be challenging since ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. Patients can estimate their insulin needs in several ways, including nutrition information from restaurants or a hand-held reference book.
Hypo- and hyperglycemia can occur more easily in situations where new or different foods are eaten; thus patients should keep a fast-acting source of carbohydrates and blood glucose monitor on hand at all times. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Surgery — Patients who undergo surgery may be instructed not to eat for eight to 12 hours before their procedure. A healthcare provider can help to determine the dose and timing of insulin before and after the procedure, especially if a patient will be unable to eat a normal diet afterwards.
Infections — Mild infections, such as a cold, sore throat, or urinary tract infection, can cause blood glucose levels to rise. In this situation, frequent telephone contact with a healthcare provider, careful blood glucose monitoring, and increasing the insulin dose are often recommended. It is important to drink an adequate amount of fluids while ill to avoid dehydration. Patients with nausea or vomiting may require medication to control their symptoms and avoid dehydration.
Travel — Managing blood glucose levels and insulin treatment while traveling can be difficult, especially when traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making careful blood glucose monitoring essential. Patients should speak with their healthcare provider before traveling to develop a treatment plan. (See "Patient information: General travel advice", section on Traveling with medical conditions).
STAYING MOTIVATED — Living with diabetes can be very demanding and some patients lose motivation over time. Healthcare providers can provide tips and encouragement to help patients stay on track. Helpful information and support is also available from the American Diabetes Association (ADA), at (800)-DIABETES (800-342-2383) and at www.diabetes.org.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
Canadian Diabetes Associates
(www.diabetes.ca)
Juvenile Diabetes Research Foundation
(www.jdrf.org)
U.S. Center for Disease Control and Prevention
(www.cdc.gov/diabetes)
[1-5]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
2. Turner, RC, Cull, CA, Frighi, V, Holman, RR for the UK Prospective Diabetes Study (UKPDS) Group. Glycemic control with diet, sulfonylurea, metformin, or insulin in patients with type 2 diabetes. Progressive requirement for multiple therapies (UKPDS 49). JAMA 1999; 281:2005.
3. Fleming, DR, Jacober, SJ, Vandenberg, MA, et al. The safety of injecting insulin through clothing. Diabetes Care 1997; 20:244.
4. Yki-Järvinen, H, Dressler, A, Ziemen, M. Less nocturnal hypoglycemia and better post-dinner glucose control with bedtime insulin glargine compared with bedtime NPH insulin during insulin combination therapy in type 2 diabetes. Diabetes Care 2000; 23:1130.
5. Taylor, R, Davies, R, Fox, C, et al. Appropriate insulin regimes for type 2 diabetes: a multicenter randomized crossover study. Diabetes Care 2000; 23:1612.
Diabetes mellitus, type 2
INTRODUCTION — Type 2 diabetes mellitus occurs when the pancreas (an organ in the abdomen) produces insufficient amounts of the hormone insulin and/or the body's tissues become resistant to normal or even high levels of insulin (show figure 1). This causes high blood glucose (sugar) levels, which can lead to a number of complications if untreated.
Type 2 diabetes is a chronic medical condition that requires regular monitoring and treatment. Treatment, which includes lifestyle adjustments, self-care measures, and sometimes medications, can control blood glucose levels in the near-normal range and minimize the risk of diabetes-related complications.
In the United States, Canada, and Europe, type 2 diabetes accounts for about 90 percent of all cases of diabetes. More than 6 percent of all people between the ages of 20 and 74 years and more than 12 percent of persons over age 40 have type 2 diabetes; these numbers continue to increase.
THE IMPACT OF DIABETES — Being diagnosed with type 2 diabetes can be a frightening and overwhelming experience for some people, and it is common to have questions about why it developed, what it means for long-term health, and how it will affect everyday life. For most people, the first few months after being diagnosed are filled with emotional highs and lows. People with newly-diagnosed diabetes, as well as their families, can use this time to learn as much as possible so that diabetes-related care (eg, self-blood glucose testing, medical appointments, daily medications) becomes a "normal" part of the daily routine.
In addition, people who are newly diagnosed should talk to their healthcare provider about resources that are available for medical as well as psychological support. This may include group classes, meetings with a nutritionist, social worker, or nurse educator, and other educational resources such as books, web sites, or magazines. Several of these resources are listed in this topic review (see "Where to get more information" below).
Despite the risks associated with type 2 diabetes, most people can lead active lives and continue to enjoy the foods and activities that they previously enjoyed. Diabetes does not mean an end to special occasion foods like birthday cake, and with a little advanced planning, most people with diabetes can enjoy exercise in almost any form.
CAUSES — Type 2 diabetes is probably caused by a complex interaction of environmental factors and predisposing genetic factors.
Genetic causes — Many people with type 2 diabetes have a family member with type 2 diabetes or conditions commonly associated with diabetes, such as high blood lipid levels, high blood pressure, or obesity. As an example, 39 percent of patients with type 2 diabetes have at least one parent with the disease. The lifetime risk that a first-degree relative (sister, brother, son, daughter) will develop diabetes is five to ten times higher than that of a person of a similar age and weight who has no family history of diabetes. Several common genetic variants have been identified. However, genetic testing is not currently recommended.
The likelihood of developing type 2 diabetes is greater in certain ethnic groups; for example, people of Hispanic, African, and Asian descent are at greater risk of developing diabetes compared to people who are white.
Environmental conditions — Environmental factors such as diet and activity levels interact with genetic causes to influence the development of type 2 diabetes. The incidence of type 2 diabetes has increased dramatically in the United States over the last 20 years as the percentage of people who are obese increases.
Pregnancy — About 3 to 5 percent of pregnant women develop gestational diabetes, usually after 24 to 28 weeks of pregnancy. Gestational diabetes is similar to type 2 diabetes, but generally resolves after a woman delivers her baby. Hormones cause an increase in insulin resistance during pregnancy, which can lead to gestational diabetes. Women who develop gestational diabetes during pregnancy are at high risk for developing type 2 diabetes later in life. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Other causes — Other, less common causes of diabetes include endocrine conditions that indirectly change the production and action of insulin and lead to diabetes. These include Cushing's syndrome, acromegaly, pheochromocytoma, hyperthyroidism and polycystic ovarian syndrome (PCOS). (See "Patient information: Cushing's syndrome" and see "Patient information: Acromegaly (somatotroph adenomas)" and see "Patient information: Hyperthyroidism" and see "Patient information: Polycystic ovary syndrome (PCOS)").
DIAGNOSIS — The diagnosis of diabetes is based upon a person's symptoms and the results of laboratory tests.
Symptoms — Before being diagnosed with diabetes, some people have symptoms of high blood glucose, including frequent urination, excessive thirst, and blurred vision. Sometimes, diabetes is discovered when a person seeks medical help for another problem (such as erectile dysfunction or pain and numbness in the feet). However, most people with type 2 diabetes have no symptoms at all, and the diagnosis is often delayed for five or more years.
Because family history is a factor in the development of type 2 diabetes, people with family members with diabetes or conditions commonly associated with diabetes, such as hypertension, high blood lipid levels, and obesity, should mention this to their healthcare provider. There are usually few signs of diabetes on a physical examination early in the course of the disease.
Laboratory tests — Several blood tests are used to measure blood glucose levels, the primary test for diagnosing diabetes. Additional tests can determine the type of diabetes and its severity. Random blood glucose test — For a random blood glucose test, blood can be drawn at any time throughout the day, regardless of when the person last ate. A random blood glucose level of 200 mg/dL (11.1 mmol/L) or higher in persons who have symptoms of high blood glucose (see "Symptoms" above) suggests a diagnosis of diabetes. Fasting blood glucose test — Fasting blood glucose testing involves measuring blood glucose after not eating or drinking for 8 to 12 hours (usually overnight). A normal fasting blood glucose level is less than 100 mg/dL. A fasting blood glucose of 126 mg/dL (7.0 mmol/L) or higher indicates diabetes. The test is done by taking a small sample of blood from a vein or fingertip. It must be repeated on another day to confirm that it remains abnormally high (see "Criteria for diagnosis" below). Hemoglobin A1C test (A1C) — The A1C blood test measures the average blood glucose level during the past two to three months. It is used to monitor blood glucose control in people with known diabetes, but is not normally used to diagnose diabetes. Normal values for A1C are 4 to 6 percent (show figure 3). The test is done by taking a small sample of blood from a vein or fingertip. Oral glucose tolerance test — Oral glucose tolerance testing (OGTT) is the most sensitive test for diagnosing diabetes and pre-diabetes. However, the OGTT is not routinely recommended because it is inconvenient compared to a fasting blood glucose test.
The standard OGTT includes a fasting blood glucose test. The person then drinks a 75 gram liquid glucose solution (which tastes very sweet, and is usually cola or orange-flavored). Two hours later, a second blood glucose level is measured.
Oral glucose tolerance testing is routinely performed at 24 to 28 weeks of pregnancy to screen for gestational diabetes; this requires drinking a 50 gram glucose solution with a blood glucose level drawn one hour later. For women who have an abnormally elevated blood glucose level, a second OGTT is performed on another day after drinking a 100 gram glucose solution. The blood glucose level is measured before, and at one, two, and three hours after drinking the solution.
Criteria for diagnosis — The following criteria are used to define a person's blood glucose levels as normal, suggestive of pre-diabetes (defined as an abnormal blood glucose level which is not high enough to be considered diabetic, but with an increased risk of diabetes in the future), or as diagnostic for diabetes. Normal — Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol/L). Pre-diabetes — Pre-diabetes can be diagnosed based upon a fasting blood glucose test or an OGTT.
- Impaired fasting glucose is defined as a fasting plasma glucose between 100 and 125 mg/dL (5.6 to 6.9 mmol/L).
- Impaired glucose tolerance is defined as a glucose level of 140 to 199 mg/dL, measured two hours after a 75 gram oral glucose tolerance test.
At least 50 percent of people with impaired glucose tolerance eventually develop type 2 diabetes, and they have an increased risk of heart disease even if diabetes does not develop. Impaired glucose tolerance is very common; about 11 percent of all people between the ages of 20 and 74 years have impaired glucose tolerance. Diabetes mellitus — A person is considered to be diabetic if he or she has one or more of the following criteria:
- Symptoms of diabetes (see "Symptoms" above) and a random blood glucose of 200 mg/dL (11.1 mmol/L) or higher
- A fasting blood glucose level of 126 mg/dL (7.0 mmol/L) or higher
- A blood glucose of 200 mg/dL (11.1 mmol/L) or higher two hours after a 75 gram oral glucose tolerance test.
The blood tests must be repeated on another day to confirm that they remain abnormally high.
Type 1 versus type 2 diabetes — A healthcare provider is usually able to determine whether a person has type 1 or type 2 diabetes, based upon the person's need for insulin (needed from the beginning in type 1, and less commonly early in type 2), and the presence of ketones in the urine when blood glucose levels are elevated (common in type 1, uncommon in type 2). Other characteristics such as older age and higher weight suggest, but do not prove, type 2 diabetes.
However, there are situations where it is less clear if a person has type 1 or 2 diabetes. In this situation, additional blood testing may be needed. When the type of diabetes is in doubt, the clinician will usually treat the patient with insulin, as if they have type 1, since it is critical to avoid a potentially dangerous condition known as diabetic ketoacidosis (DKA). People with type 2 diabetes do not usually develop DKA. (See "Patient information: Diabetes mellitus, type 1").
TREATMENT — A full discussion of the treatment for type 2 diabetes is available separately. (See "Patient information: Diabetes type 2: Treatment" and see "Patient information: Diabetes type 2: Insulin treatment").
COMPLICATIONS — Complications of type 2 diabetes may be related to the disease itself or to the treatments necessary to manage diabetes. (See "Patient information: Preventing complications in diabetes mellitus").
Diabetes-related complications — The most common long-term complication of type 2 diabetes is cardiovascular (heart) disease, which can cause heart attack, angina (chest pain), stroke, and even death. The risk of heart disease in people with diabetes is estimated to be at least twice that of people without diabetes.
However, people with type 2 diabetes can substantially lower their risk of cardiovascular disease by quitting smoking, taking a low-dose aspirin every day, and by managing their high blood pressure and hyperlipidemia with diet, exercise, and medications (show figure 2). (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and see "Patient information: High blood pressure treatment" and see "Patient information: Smoking cessation" and see "Patient information: Aspirin and heart disease").
People with type 2 diabetes are also at increased risk of developing eye, kidney, and nerve complications that can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. These complications occur after many years of diabetes and are related to elevated blood glucose levels over time. These complications can be prevented or delayed by keeping blood sugar levels as close to normal as possible and by carefully controlling blood pressure. Diabetes remains the greatest cause of blindness, kidney failure, and amputations in the United States and in much of the world.
Treatment-related complications — The most common treatment-related complication of type 2 diabetes is weight gain. This occurs most commonly in people who use certain oral diabetes medications and in those who take insulin. The oral medication metformin is not associated with weight gain.
Weight gain can be prevented or managed with regular exercise and careful attention to diet. Some patients with type 2 diabetes who are significantly overweight benefit from medications or surgery to improve their chances of losing weight. (See "Patient information: Weight loss treatments" and see "Patient information: Weight loss surgery").
PREGNANCY AND DIABETES — Women with type 2 diabetes are usually able to become pregnant and have a healthy baby. However, it is important to tightly control blood glucose levels before and during pregnancy to minimize the risk of complications. A full discussion of this topic is available separately. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Endocrine Society
(www.endo-society.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
[1-7]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Knowler, WC, Barrett-Connor, E, Fowler, SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002; 346:393.
2. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854.
3. Kjos, SL, Peters, RK, Xiang, A, et al. Predicting future diabetes in Latino women with gestational diabetes: Utility of early postpartum glucose tolerance testing. Diabetes 1995; 44:586.
4. Selvin, E, Coresh, J, Golden, SH, et al. Glycemic control, atherosclerosis, and risk factors for cardiovascular disease in individuals with diabetes: the atherosclerosis risk in communities study. Diabetes Care 2005; 28:1965.
5. Meigs, JB, Singer, DE, Sullivan, LM, et al. Metabolic control and prevalent cardiovascular disease in non-insulin-dependent diabetes mellitus (NIDDM): the NIDDM Patient Outcomes Research Team. Am J Med 1997; 102:38.
6. Selvin, E, Wattanakit, K, Steffes, MW, et al. HbA1c and Peripheral Arterial Disease in Diabetes: The Atherosclerosis Risk in Communities study. Diabetes Care 2006; 29:877.
7. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
Type 2 diabetes is a chronic medical condition that requires regular monitoring and treatment. Treatment, which includes lifestyle adjustments, self-care measures, and sometimes medications, can control blood glucose levels in the near-normal range and minimize the risk of diabetes-related complications.
In the United States, Canada, and Europe, type 2 diabetes accounts for about 90 percent of all cases of diabetes. More than 6 percent of all people between the ages of 20 and 74 years and more than 12 percent of persons over age 40 have type 2 diabetes; these numbers continue to increase.
THE IMPACT OF DIABETES — Being diagnosed with type 2 diabetes can be a frightening and overwhelming experience for some people, and it is common to have questions about why it developed, what it means for long-term health, and how it will affect everyday life. For most people, the first few months after being diagnosed are filled with emotional highs and lows. People with newly-diagnosed diabetes, as well as their families, can use this time to learn as much as possible so that diabetes-related care (eg, self-blood glucose testing, medical appointments, daily medications) becomes a "normal" part of the daily routine.
In addition, people who are newly diagnosed should talk to their healthcare provider about resources that are available for medical as well as psychological support. This may include group classes, meetings with a nutritionist, social worker, or nurse educator, and other educational resources such as books, web sites, or magazines. Several of these resources are listed in this topic review (see "Where to get more information" below).
Despite the risks associated with type 2 diabetes, most people can lead active lives and continue to enjoy the foods and activities that they previously enjoyed. Diabetes does not mean an end to special occasion foods like birthday cake, and with a little advanced planning, most people with diabetes can enjoy exercise in almost any form.
CAUSES — Type 2 diabetes is probably caused by a complex interaction of environmental factors and predisposing genetic factors.
Genetic causes — Many people with type 2 diabetes have a family member with type 2 diabetes or conditions commonly associated with diabetes, such as high blood lipid levels, high blood pressure, or obesity. As an example, 39 percent of patients with type 2 diabetes have at least one parent with the disease. The lifetime risk that a first-degree relative (sister, brother, son, daughter) will develop diabetes is five to ten times higher than that of a person of a similar age and weight who has no family history of diabetes. Several common genetic variants have been identified. However, genetic testing is not currently recommended.
The likelihood of developing type 2 diabetes is greater in certain ethnic groups; for example, people of Hispanic, African, and Asian descent are at greater risk of developing diabetes compared to people who are white.
Environmental conditions — Environmental factors such as diet and activity levels interact with genetic causes to influence the development of type 2 diabetes. The incidence of type 2 diabetes has increased dramatically in the United States over the last 20 years as the percentage of people who are obese increases.
Pregnancy — About 3 to 5 percent of pregnant women develop gestational diabetes, usually after 24 to 28 weeks of pregnancy. Gestational diabetes is similar to type 2 diabetes, but generally resolves after a woman delivers her baby. Hormones cause an increase in insulin resistance during pregnancy, which can lead to gestational diabetes. Women who develop gestational diabetes during pregnancy are at high risk for developing type 2 diabetes later in life. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Other causes — Other, less common causes of diabetes include endocrine conditions that indirectly change the production and action of insulin and lead to diabetes. These include Cushing's syndrome, acromegaly, pheochromocytoma, hyperthyroidism and polycystic ovarian syndrome (PCOS). (See "Patient information: Cushing's syndrome" and see "Patient information: Acromegaly (somatotroph adenomas)" and see "Patient information: Hyperthyroidism" and see "Patient information: Polycystic ovary syndrome (PCOS)").
DIAGNOSIS — The diagnosis of diabetes is based upon a person's symptoms and the results of laboratory tests.
Symptoms — Before being diagnosed with diabetes, some people have symptoms of high blood glucose, including frequent urination, excessive thirst, and blurred vision. Sometimes, diabetes is discovered when a person seeks medical help for another problem (such as erectile dysfunction or pain and numbness in the feet). However, most people with type 2 diabetes have no symptoms at all, and the diagnosis is often delayed for five or more years.
Because family history is a factor in the development of type 2 diabetes, people with family members with diabetes or conditions commonly associated with diabetes, such as hypertension, high blood lipid levels, and obesity, should mention this to their healthcare provider. There are usually few signs of diabetes on a physical examination early in the course of the disease.
Laboratory tests — Several blood tests are used to measure blood glucose levels, the primary test for diagnosing diabetes. Additional tests can determine the type of diabetes and its severity. Random blood glucose test — For a random blood glucose test, blood can be drawn at any time throughout the day, regardless of when the person last ate. A random blood glucose level of 200 mg/dL (11.1 mmol/L) or higher in persons who have symptoms of high blood glucose (see "Symptoms" above) suggests a diagnosis of diabetes. Fasting blood glucose test — Fasting blood glucose testing involves measuring blood glucose after not eating or drinking for 8 to 12 hours (usually overnight). A normal fasting blood glucose level is less than 100 mg/dL. A fasting blood glucose of 126 mg/dL (7.0 mmol/L) or higher indicates diabetes. The test is done by taking a small sample of blood from a vein or fingertip. It must be repeated on another day to confirm that it remains abnormally high (see "Criteria for diagnosis" below). Hemoglobin A1C test (A1C) — The A1C blood test measures the average blood glucose level during the past two to three months. It is used to monitor blood glucose control in people with known diabetes, but is not normally used to diagnose diabetes. Normal values for A1C are 4 to 6 percent (show figure 3). The test is done by taking a small sample of blood from a vein or fingertip. Oral glucose tolerance test — Oral glucose tolerance testing (OGTT) is the most sensitive test for diagnosing diabetes and pre-diabetes. However, the OGTT is not routinely recommended because it is inconvenient compared to a fasting blood glucose test.
The standard OGTT includes a fasting blood glucose test. The person then drinks a 75 gram liquid glucose solution (which tastes very sweet, and is usually cola or orange-flavored). Two hours later, a second blood glucose level is measured.
Oral glucose tolerance testing is routinely performed at 24 to 28 weeks of pregnancy to screen for gestational diabetes; this requires drinking a 50 gram glucose solution with a blood glucose level drawn one hour later. For women who have an abnormally elevated blood glucose level, a second OGTT is performed on another day after drinking a 100 gram glucose solution. The blood glucose level is measured before, and at one, two, and three hours after drinking the solution.
Criteria for diagnosis — The following criteria are used to define a person's blood glucose levels as normal, suggestive of pre-diabetes (defined as an abnormal blood glucose level which is not high enough to be considered diabetic, but with an increased risk of diabetes in the future), or as diagnostic for diabetes. Normal — Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol/L). Pre-diabetes — Pre-diabetes can be diagnosed based upon a fasting blood glucose test or an OGTT.
- Impaired fasting glucose is defined as a fasting plasma glucose between 100 and 125 mg/dL (5.6 to 6.9 mmol/L).
- Impaired glucose tolerance is defined as a glucose level of 140 to 199 mg/dL, measured two hours after a 75 gram oral glucose tolerance test.
At least 50 percent of people with impaired glucose tolerance eventually develop type 2 diabetes, and they have an increased risk of heart disease even if diabetes does not develop. Impaired glucose tolerance is very common; about 11 percent of all people between the ages of 20 and 74 years have impaired glucose tolerance. Diabetes mellitus — A person is considered to be diabetic if he or she has one or more of the following criteria:
- Symptoms of diabetes (see "Symptoms" above) and a random blood glucose of 200 mg/dL (11.1 mmol/L) or higher
- A fasting blood glucose level of 126 mg/dL (7.0 mmol/L) or higher
- A blood glucose of 200 mg/dL (11.1 mmol/L) or higher two hours after a 75 gram oral glucose tolerance test.
The blood tests must be repeated on another day to confirm that they remain abnormally high.
Type 1 versus type 2 diabetes — A healthcare provider is usually able to determine whether a person has type 1 or type 2 diabetes, based upon the person's need for insulin (needed from the beginning in type 1, and less commonly early in type 2), and the presence of ketones in the urine when blood glucose levels are elevated (common in type 1, uncommon in type 2). Other characteristics such as older age and higher weight suggest, but do not prove, type 2 diabetes.
However, there are situations where it is less clear if a person has type 1 or 2 diabetes. In this situation, additional blood testing may be needed. When the type of diabetes is in doubt, the clinician will usually treat the patient with insulin, as if they have type 1, since it is critical to avoid a potentially dangerous condition known as diabetic ketoacidosis (DKA). People with type 2 diabetes do not usually develop DKA. (See "Patient information: Diabetes mellitus, type 1").
TREATMENT — A full discussion of the treatment for type 2 diabetes is available separately. (See "Patient information: Diabetes type 2: Treatment" and see "Patient information: Diabetes type 2: Insulin treatment").
COMPLICATIONS — Complications of type 2 diabetes may be related to the disease itself or to the treatments necessary to manage diabetes. (See "Patient information: Preventing complications in diabetes mellitus").
Diabetes-related complications — The most common long-term complication of type 2 diabetes is cardiovascular (heart) disease, which can cause heart attack, angina (chest pain), stroke, and even death. The risk of heart disease in people with diabetes is estimated to be at least twice that of people without diabetes.
However, people with type 2 diabetes can substantially lower their risk of cardiovascular disease by quitting smoking, taking a low-dose aspirin every day, and by managing their high blood pressure and hyperlipidemia with diet, exercise, and medications (show figure 2). (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and see "Patient information: High blood pressure treatment" and see "Patient information: Smoking cessation" and see "Patient information: Aspirin and heart disease").
People with type 2 diabetes are also at increased risk of developing eye, kidney, and nerve complications that can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. These complications occur after many years of diabetes and are related to elevated blood glucose levels over time. These complications can be prevented or delayed by keeping blood sugar levels as close to normal as possible and by carefully controlling blood pressure. Diabetes remains the greatest cause of blindness, kidney failure, and amputations in the United States and in much of the world.
Treatment-related complications — The most common treatment-related complication of type 2 diabetes is weight gain. This occurs most commonly in people who use certain oral diabetes medications and in those who take insulin. The oral medication metformin is not associated with weight gain.
Weight gain can be prevented or managed with regular exercise and careful attention to diet. Some patients with type 2 diabetes who are significantly overweight benefit from medications or surgery to improve their chances of losing weight. (See "Patient information: Weight loss treatments" and see "Patient information: Weight loss surgery").
PREGNANCY AND DIABETES — Women with type 2 diabetes are usually able to become pregnant and have a healthy baby. However, it is important to tightly control blood glucose levels before and during pregnancy to minimize the risk of complications. A full discussion of this topic is available separately. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Endocrine Society
(www.endo-society.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
[1-7]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Knowler, WC, Barrett-Connor, E, Fowler, SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002; 346:393.
2. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854.
3. Kjos, SL, Peters, RK, Xiang, A, et al. Predicting future diabetes in Latino women with gestational diabetes: Utility of early postpartum glucose tolerance testing. Diabetes 1995; 44:586.
4. Selvin, E, Coresh, J, Golden, SH, et al. Glycemic control, atherosclerosis, and risk factors for cardiovascular disease in individuals with diabetes: the atherosclerosis risk in communities study. Diabetes Care 2005; 28:1965.
5. Meigs, JB, Singer, DE, Sullivan, LM, et al. Metabolic control and prevalent cardiovascular disease in non-insulin-dependent diabetes mellitus (NIDDM): the NIDDM Patient Outcomes Research Team. Am J Med 1997; 102:38.
6. Selvin, E, Wattanakit, K, Steffes, MW, et al. HbA1c and Peripheral Arterial Disease in Diabetes: The Atherosclerosis Risk in Communities study. Diabetes Care 2006; 29:877.
7. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
Diabetes mellitus, type 2
INTRODUCTION — Type 2 diabetes mellitus occurs when the pancreas (an organ in the abdomen) produces insufficient amounts of the hormone insulin and/or the body's tissues become resistant to normal or even high levels of insulin (show figure 1). This causes high blood glucose (sugar) levels, which can lead to a number of complications if untreated.
Type 2 diabetes is a chronic medical condition that requires regular monitoring and treatment. Treatment, which includes lifestyle adjustments, self-care measures, and sometimes medications, can control blood glucose levels in the near-normal range and minimize the risk of diabetes-related complications.
In the United States, Canada, and Europe, type 2 diabetes accounts for about 90 percent of all cases of diabetes. More than 6 percent of all people between the ages of 20 and 74 years and more than 12 percent of persons over age 40 have type 2 diabetes; these numbers continue to increase.
THE IMPACT OF DIABETES — Being diagnosed with type 2 diabetes can be a frightening and overwhelming experience for some people, and it is common to have questions about why it developed, what it means for long-term health, and how it will affect everyday life. For most people, the first few months after being diagnosed are filled with emotional highs and lows. People with newly-diagnosed diabetes, as well as their families, can use this time to learn as much as possible so that diabetes-related care (eg, self-blood glucose testing, medical appointments, daily medications) becomes a "normal" part of the daily routine.
In addition, people who are newly diagnosed should talk to their healthcare provider about resources that are available for medical as well as psychological support. This may include group classes, meetings with a nutritionist, social worker, or nurse educator, and other educational resources such as books, web sites, or magazines. Several of these resources are listed in this topic review (see "Where to get more information" below).
Despite the risks associated with type 2 diabetes, most people can lead active lives and continue to enjoy the foods and activities that they previously enjoyed. Diabetes does not mean an end to special occasion foods like birthday cake, and with a little advanced planning, most people with diabetes can enjoy exercise in almost any form.
CAUSES — Type 2 diabetes is probably caused by a complex interaction of environmental factors and predisposing genetic factors.
Genetic causes — Many people with type 2 diabetes have a family member with type 2 diabetes or conditions commonly associated with diabetes, such as high blood lipid levels, high blood pressure, or obesity. As an example, 39 percent of patients with type 2 diabetes have at least one parent with the disease. The lifetime risk that a first-degree relative (sister, brother, son, daughter) will develop diabetes is five to ten times higher than that of a person of a similar age and weight who has no family history of diabetes. Several common genetic variants have been identified. However, genetic testing is not currently recommended.
The likelihood of developing type 2 diabetes is greater in certain ethnic groups; for example, people of Hispanic, African, and Asian descent are at greater risk of developing diabetes compared to people who are white.
Environmental conditions — Environmental factors such as diet and activity levels interact with genetic causes to influence the development of type 2 diabetes. The incidence of type 2 diabetes has increased dramatically in the United States over the last 20 years as the percentage of people who are obese increases.
Pregnancy — About 3 to 5 percent of pregnant women develop gestational diabetes, usually after 24 to 28 weeks of pregnancy. Gestational diabetes is similar to type 2 diabetes, but generally resolves after a woman delivers her baby. Hormones cause an increase in insulin resistance during pregnancy, which can lead to gestational diabetes. Women who develop gestational diabetes during pregnancy are at high risk for developing type 2 diabetes later in life. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Other causes — Other, less common causes of diabetes include endocrine conditions that indirectly change the production and action of insulin and lead to diabetes. These include Cushing's syndrome, acromegaly, pheochromocytoma, hyperthyroidism and polycystic ovarian syndrome (PCOS). (See "Patient information: Cushing's syndrome" and see "Patient information: Acromegaly (somatotroph adenomas)" and see "Patient information: Hyperthyroidism" and see "Patient information: Polycystic ovary syndrome (PCOS)").
DIAGNOSIS — The diagnosis of diabetes is based upon a person's symptoms and the results of laboratory tests.
Symptoms — Before being diagnosed with diabetes, some people have symptoms of high blood glucose, including frequent urination, excessive thirst, and blurred vision. Sometimes, diabetes is discovered when a person seeks medical help for another problem (such as erectile dysfunction or pain and numbness in the feet). However, most people with type 2 diabetes have no symptoms at all, and the diagnosis is often delayed for five or more years.
Because family history is a factor in the development of type 2 diabetes, people with family members with diabetes or conditions commonly associated with diabetes, such as hypertension, high blood lipid levels, and obesity, should mention this to their healthcare provider. There are usually few signs of diabetes on a physical examination early in the course of the disease.
Laboratory tests — Several blood tests are used to measure blood glucose levels, the primary test for diagnosing diabetes. Additional tests can determine the type of diabetes and its severity. Random blood glucose test — For a random blood glucose test, blood can be drawn at any time throughout the day, regardless of when the person last ate. A random blood glucose level of 200 mg/dL (11.1 mmol/L) or higher in persons who have symptoms of high blood glucose (see "Symptoms" above) suggests a diagnosis of diabetes. Fasting blood glucose test — Fasting blood glucose testing involves measuring blood glucose after not eating or drinking for 8 to 12 hours (usually overnight). A normal fasting blood glucose level is less than 100 mg/dL. A fasting blood glucose of 126 mg/dL (7.0 mmol/L) or higher indicates diabetes. The test is done by taking a small sample of blood from a vein or fingertip. It must be repeated on another day to confirm that it remains abnormally high (see "Criteria for diagnosis" below). Hemoglobin A1C test (A1C) — The A1C blood test measures the average blood glucose level during the past two to three months. It is used to monitor blood glucose control in people with known diabetes, but is not normally used to diagnose diabetes. Normal values for A1C are 4 to 6 percent (show figure 3). The test is done by taking a small sample of blood from a vein or fingertip. Oral glucose tolerance test — Oral glucose tolerance testing (OGTT) is the most sensitive test for diagnosing diabetes and pre-diabetes. However, the OGTT is not routinely recommended because it is inconvenient compared to a fasting blood glucose test.
The standard OGTT includes a fasting blood glucose test. The person then drinks a 75 gram liquid glucose solution (which tastes very sweet, and is usually cola or orange-flavored). Two hours later, a second blood glucose level is measured.
Oral glucose tolerance testing is routinely performed at 24 to 28 weeks of pregnancy to screen for gestational diabetes; this requires drinking a 50 gram glucose solution with a blood glucose level drawn one hour later. For women who have an abnormally elevated blood glucose level, a second OGTT is performed on another day after drinking a 100 gram glucose solution. The blood glucose level is measured before, and at one, two, and three hours after drinking the solution.
Criteria for diagnosis — The following criteria are used to define a person's blood glucose levels as normal, suggestive of pre-diabetes (defined as an abnormal blood glucose level which is not high enough to be considered diabetic, but with an increased risk of diabetes in the future), or as diagnostic for diabetes. Normal — Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol/L). Pre-diabetes — Pre-diabetes can be diagnosed based upon a fasting blood glucose test or an OGTT.
- Impaired fasting glucose is defined as a fasting plasma glucose between 100 and 125 mg/dL (5.6 to 6.9 mmol/L).
- Impaired glucose tolerance is defined as a glucose level of 140 to 199 mg/dL, measured two hours after a 75 gram oral glucose tolerance test.
At least 50 percent of people with impaired glucose tolerance eventually develop type 2 diabetes, and they have an increased risk of heart disease even if diabetes does not develop. Impaired glucose tolerance is very common; about 11 percent of all people between the ages of 20 and 74 years have impaired glucose tolerance. Diabetes mellitus — A person is considered to be diabetic if he or she has one or more of the following criteria:
- Symptoms of diabetes (see "Symptoms" above) and a random blood glucose of 200 mg/dL (11.1 mmol/L) or higher
- A fasting blood glucose level of 126 mg/dL (7.0 mmol/L) or higher
- A blood glucose of 200 mg/dL (11.1 mmol/L) or higher two hours after a 75 gram oral glucose tolerance test.
The blood tests must be repeated on another day to confirm that they remain abnormally high.
Type 1 versus type 2 diabetes — A healthcare provider is usually able to determine whether a person has type 1 or type 2 diabetes, based upon the person's need for insulin (needed from the beginning in type 1, and less commonly early in type 2), and the presence of ketones in the urine when blood glucose levels are elevated (common in type 1, uncommon in type 2). Other characteristics such as older age and higher weight suggest, but do not prove, type 2 diabetes.
However, there are situations where it is less clear if a person has type 1 or 2 diabetes. In this situation, additional blood testing may be needed. When the type of diabetes is in doubt, the clinician will usually treat the patient with insulin, as if they have type 1, since it is critical to avoid a potentially dangerous condition known as diabetic ketoacidosis (DKA). People with type 2 diabetes do not usually develop DKA. (See "Patient information: Diabetes mellitus, type 1").
TREATMENT — A full discussion of the treatment for type 2 diabetes is available separately. (See "Patient information: Diabetes type 2: Treatment" and see "Patient information: Diabetes type 2: Insulin treatment").
COMPLICATIONS — Complications of type 2 diabetes may be related to the disease itself or to the treatments necessary to manage diabetes. (See "Patient information: Preventing complications in diabetes mellitus").
Diabetes-related complications — The most common long-term complication of type 2 diabetes is cardiovascular (heart) disease, which can cause heart attack, angina (chest pain), stroke, and even death. The risk of heart disease in people with diabetes is estimated to be at least twice that of people without diabetes.
However, people with type 2 diabetes can substantially lower their risk of cardiovascular disease by quitting smoking, taking a low-dose aspirin every day, and by managing their high blood pressure and hyperlipidemia with diet, exercise, and medications (show figure 2). (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and see "Patient information: High blood pressure treatment" and see "Patient information: Smoking cessation" and see "Patient information: Aspirin and heart disease").
People with type 2 diabetes are also at increased risk of developing eye, kidney, and nerve complications that can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. These complications occur after many years of diabetes and are related to elevated blood glucose levels over time. These complications can be prevented or delayed by keeping blood sugar levels as close to normal as possible and by carefully controlling blood pressure. Diabetes remains the greatest cause of blindness, kidney failure, and amputations in the United States and in much of the world.
Treatment-related complications — The most common treatment-related complication of type 2 diabetes is weight gain. This occurs most commonly in people who use certain oral diabetes medications and in those who take insulin. The oral medication metformin is not associated with weight gain.
Weight gain can be prevented or managed with regular exercise and careful attention to diet. Some patients with type 2 diabetes who are significantly overweight benefit from medications or surgery to improve their chances of losing weight. (See "Patient information: Weight loss treatments" and see "Patient information: Weight loss surgery").
PREGNANCY AND DIABETES — Women with type 2 diabetes are usually able to become pregnant and have a healthy baby. However, it is important to tightly control blood glucose levels before and during pregnancy to minimize the risk of complications. A full discussion of this topic is available separately. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Endocrine Society
(www.endo-society.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
[1-7]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Knowler, WC, Barrett-Connor, E, Fowler, SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002; 346:393.
2. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854.
3. Kjos, SL, Peters, RK, Xiang, A, et al. Predicting future diabetes in Latino women with gestational diabetes: Utility of early postpartum glucose tolerance testing. Diabetes 1995; 44:586.
4. Selvin, E, Coresh, J, Golden, SH, et al. Glycemic control, atherosclerosis, and risk factors for cardiovascular disease in individuals with diabetes: the atherosclerosis risk in communities study. Diabetes Care 2005; 28:1965.
5. Meigs, JB, Singer, DE, Sullivan, LM, et al. Metabolic control and prevalent cardiovascular disease in non-insulin-dependent diabetes mellitus (NIDDM): the NIDDM Patient Outcomes Research Team. Am J Med 1997; 102:38.
6. Selvin, E, Wattanakit, K, Steffes, MW, et al. HbA1c and Peripheral Arterial Disease in Diabetes: The Atherosclerosis Risk in Communities study. Diabetes Care 2006; 29:877.
7. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
Type 2 diabetes is a chronic medical condition that requires regular monitoring and treatment. Treatment, which includes lifestyle adjustments, self-care measures, and sometimes medications, can control blood glucose levels in the near-normal range and minimize the risk of diabetes-related complications.
In the United States, Canada, and Europe, type 2 diabetes accounts for about 90 percent of all cases of diabetes. More than 6 percent of all people between the ages of 20 and 74 years and more than 12 percent of persons over age 40 have type 2 diabetes; these numbers continue to increase.
THE IMPACT OF DIABETES — Being diagnosed with type 2 diabetes can be a frightening and overwhelming experience for some people, and it is common to have questions about why it developed, what it means for long-term health, and how it will affect everyday life. For most people, the first few months after being diagnosed are filled with emotional highs and lows. People with newly-diagnosed diabetes, as well as their families, can use this time to learn as much as possible so that diabetes-related care (eg, self-blood glucose testing, medical appointments, daily medications) becomes a "normal" part of the daily routine.
In addition, people who are newly diagnosed should talk to their healthcare provider about resources that are available for medical as well as psychological support. This may include group classes, meetings with a nutritionist, social worker, or nurse educator, and other educational resources such as books, web sites, or magazines. Several of these resources are listed in this topic review (see "Where to get more information" below).
Despite the risks associated with type 2 diabetes, most people can lead active lives and continue to enjoy the foods and activities that they previously enjoyed. Diabetes does not mean an end to special occasion foods like birthday cake, and with a little advanced planning, most people with diabetes can enjoy exercise in almost any form.
CAUSES — Type 2 diabetes is probably caused by a complex interaction of environmental factors and predisposing genetic factors.
Genetic causes — Many people with type 2 diabetes have a family member with type 2 diabetes or conditions commonly associated with diabetes, such as high blood lipid levels, high blood pressure, or obesity. As an example, 39 percent of patients with type 2 diabetes have at least one parent with the disease. The lifetime risk that a first-degree relative (sister, brother, son, daughter) will develop diabetes is five to ten times higher than that of a person of a similar age and weight who has no family history of diabetes. Several common genetic variants have been identified. However, genetic testing is not currently recommended.
The likelihood of developing type 2 diabetes is greater in certain ethnic groups; for example, people of Hispanic, African, and Asian descent are at greater risk of developing diabetes compared to people who are white.
Environmental conditions — Environmental factors such as diet and activity levels interact with genetic causes to influence the development of type 2 diabetes. The incidence of type 2 diabetes has increased dramatically in the United States over the last 20 years as the percentage of people who are obese increases.
Pregnancy — About 3 to 5 percent of pregnant women develop gestational diabetes, usually after 24 to 28 weeks of pregnancy. Gestational diabetes is similar to type 2 diabetes, but generally resolves after a woman delivers her baby. Hormones cause an increase in insulin resistance during pregnancy, which can lead to gestational diabetes. Women who develop gestational diabetes during pregnancy are at high risk for developing type 2 diabetes later in life. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Other causes — Other, less common causes of diabetes include endocrine conditions that indirectly change the production and action of insulin and lead to diabetes. These include Cushing's syndrome, acromegaly, pheochromocytoma, hyperthyroidism and polycystic ovarian syndrome (PCOS). (See "Patient information: Cushing's syndrome" and see "Patient information: Acromegaly (somatotroph adenomas)" and see "Patient information: Hyperthyroidism" and see "Patient information: Polycystic ovary syndrome (PCOS)").
DIAGNOSIS — The diagnosis of diabetes is based upon a person's symptoms and the results of laboratory tests.
Symptoms — Before being diagnosed with diabetes, some people have symptoms of high blood glucose, including frequent urination, excessive thirst, and blurred vision. Sometimes, diabetes is discovered when a person seeks medical help for another problem (such as erectile dysfunction or pain and numbness in the feet). However, most people with type 2 diabetes have no symptoms at all, and the diagnosis is often delayed for five or more years.
Because family history is a factor in the development of type 2 diabetes, people with family members with diabetes or conditions commonly associated with diabetes, such as hypertension, high blood lipid levels, and obesity, should mention this to their healthcare provider. There are usually few signs of diabetes on a physical examination early in the course of the disease.
Laboratory tests — Several blood tests are used to measure blood glucose levels, the primary test for diagnosing diabetes. Additional tests can determine the type of diabetes and its severity. Random blood glucose test — For a random blood glucose test, blood can be drawn at any time throughout the day, regardless of when the person last ate. A random blood glucose level of 200 mg/dL (11.1 mmol/L) or higher in persons who have symptoms of high blood glucose (see "Symptoms" above) suggests a diagnosis of diabetes. Fasting blood glucose test — Fasting blood glucose testing involves measuring blood glucose after not eating or drinking for 8 to 12 hours (usually overnight). A normal fasting blood glucose level is less than 100 mg/dL. A fasting blood glucose of 126 mg/dL (7.0 mmol/L) or higher indicates diabetes. The test is done by taking a small sample of blood from a vein or fingertip. It must be repeated on another day to confirm that it remains abnormally high (see "Criteria for diagnosis" below). Hemoglobin A1C test (A1C) — The A1C blood test measures the average blood glucose level during the past two to three months. It is used to monitor blood glucose control in people with known diabetes, but is not normally used to diagnose diabetes. Normal values for A1C are 4 to 6 percent (show figure 3). The test is done by taking a small sample of blood from a vein or fingertip. Oral glucose tolerance test — Oral glucose tolerance testing (OGTT) is the most sensitive test for diagnosing diabetes and pre-diabetes. However, the OGTT is not routinely recommended because it is inconvenient compared to a fasting blood glucose test.
The standard OGTT includes a fasting blood glucose test. The person then drinks a 75 gram liquid glucose solution (which tastes very sweet, and is usually cola or orange-flavored). Two hours later, a second blood glucose level is measured.
Oral glucose tolerance testing is routinely performed at 24 to 28 weeks of pregnancy to screen for gestational diabetes; this requires drinking a 50 gram glucose solution with a blood glucose level drawn one hour later. For women who have an abnormally elevated blood glucose level, a second OGTT is performed on another day after drinking a 100 gram glucose solution. The blood glucose level is measured before, and at one, two, and three hours after drinking the solution.
Criteria for diagnosis — The following criteria are used to define a person's blood glucose levels as normal, suggestive of pre-diabetes (defined as an abnormal blood glucose level which is not high enough to be considered diabetic, but with an increased risk of diabetes in the future), or as diagnostic for diabetes. Normal — Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol/L). Pre-diabetes — Pre-diabetes can be diagnosed based upon a fasting blood glucose test or an OGTT.
- Impaired fasting glucose is defined as a fasting plasma glucose between 100 and 125 mg/dL (5.6 to 6.9 mmol/L).
- Impaired glucose tolerance is defined as a glucose level of 140 to 199 mg/dL, measured two hours after a 75 gram oral glucose tolerance test.
At least 50 percent of people with impaired glucose tolerance eventually develop type 2 diabetes, and they have an increased risk of heart disease even if diabetes does not develop. Impaired glucose tolerance is very common; about 11 percent of all people between the ages of 20 and 74 years have impaired glucose tolerance. Diabetes mellitus — A person is considered to be diabetic if he or she has one or more of the following criteria:
- Symptoms of diabetes (see "Symptoms" above) and a random blood glucose of 200 mg/dL (11.1 mmol/L) or higher
- A fasting blood glucose level of 126 mg/dL (7.0 mmol/L) or higher
- A blood glucose of 200 mg/dL (11.1 mmol/L) or higher two hours after a 75 gram oral glucose tolerance test.
The blood tests must be repeated on another day to confirm that they remain abnormally high.
Type 1 versus type 2 diabetes — A healthcare provider is usually able to determine whether a person has type 1 or type 2 diabetes, based upon the person's need for insulin (needed from the beginning in type 1, and less commonly early in type 2), and the presence of ketones in the urine when blood glucose levels are elevated (common in type 1, uncommon in type 2). Other characteristics such as older age and higher weight suggest, but do not prove, type 2 diabetes.
However, there are situations where it is less clear if a person has type 1 or 2 diabetes. In this situation, additional blood testing may be needed. When the type of diabetes is in doubt, the clinician will usually treat the patient with insulin, as if they have type 1, since it is critical to avoid a potentially dangerous condition known as diabetic ketoacidosis (DKA). People with type 2 diabetes do not usually develop DKA. (See "Patient information: Diabetes mellitus, type 1").
TREATMENT — A full discussion of the treatment for type 2 diabetes is available separately. (See "Patient information: Diabetes type 2: Treatment" and see "Patient information: Diabetes type 2: Insulin treatment").
COMPLICATIONS — Complications of type 2 diabetes may be related to the disease itself or to the treatments necessary to manage diabetes. (See "Patient information: Preventing complications in diabetes mellitus").
Diabetes-related complications — The most common long-term complication of type 2 diabetes is cardiovascular (heart) disease, which can cause heart attack, angina (chest pain), stroke, and even death. The risk of heart disease in people with diabetes is estimated to be at least twice that of people without diabetes.
However, people with type 2 diabetes can substantially lower their risk of cardiovascular disease by quitting smoking, taking a low-dose aspirin every day, and by managing their high blood pressure and hyperlipidemia with diet, exercise, and medications (show figure 2). (See "Patient information: High cholesterol and lipids (hyperlipidemia)" and see "Patient information: High blood pressure treatment" and see "Patient information: Smoking cessation" and see "Patient information: Aspirin and heart disease").
People with type 2 diabetes are also at increased risk of developing eye, kidney, and nerve complications that can result in blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. These complications occur after many years of diabetes and are related to elevated blood glucose levels over time. These complications can be prevented or delayed by keeping blood sugar levels as close to normal as possible and by carefully controlling blood pressure. Diabetes remains the greatest cause of blindness, kidney failure, and amputations in the United States and in much of the world.
Treatment-related complications — The most common treatment-related complication of type 2 diabetes is weight gain. This occurs most commonly in people who use certain oral diabetes medications and in those who take insulin. The oral medication metformin is not associated with weight gain.
Weight gain can be prevented or managed with regular exercise and careful attention to diet. Some patients with type 2 diabetes who are significantly overweight benefit from medications or surgery to improve their chances of losing weight. (See "Patient information: Weight loss treatments" and see "Patient information: Weight loss surgery").
PREGNANCY AND DIABETES — Women with type 2 diabetes are usually able to become pregnant and have a healthy baby. However, it is important to tightly control blood glucose levels before and during pregnancy to minimize the risk of complications. A full discussion of this topic is available separately. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Endocrine Society
(www.endo-society.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
[1-7]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Knowler, WC, Barrett-Connor, E, Fowler, SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002; 346:393.
2. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:854.
3. Kjos, SL, Peters, RK, Xiang, A, et al. Predicting future diabetes in Latino women with gestational diabetes: Utility of early postpartum glucose tolerance testing. Diabetes 1995; 44:586.
4. Selvin, E, Coresh, J, Golden, SH, et al. Glycemic control, atherosclerosis, and risk factors for cardiovascular disease in individuals with diabetes: the atherosclerosis risk in communities study. Diabetes Care 2005; 28:1965.
5. Meigs, JB, Singer, DE, Sullivan, LM, et al. Metabolic control and prevalent cardiovascular disease in non-insulin-dependent diabetes mellitus (NIDDM): the NIDDM Patient Outcomes Research Team. Am J Med 1997; 102:38.
6. Selvin, E, Wattanakit, K, Steffes, MW, et al. HbA1c and Peripheral Arterial Disease in Diabetes: The Atherosclerosis Risk in Communities study. Diabetes Care 2006; 29:877.
7. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998; 352:837.
Preventing complications in diabetes mellitus
INTRODUCTION — Diabetes mellitus is a chronic condition that can lead to complications over time. These complications include: Coronary heart disease, which can lead to a heart attack Cerebrovascular disease, which can lead to stroke Retinopathy (disease of the eye), which can lead to blindness Nephropathy (disease of the kidney), which can lead to kidney failure and the need for dialysis Neuropathy (disease of the nerves), which can lead to, among other things, ulceration of the foot requiring amputation
Many of these complications produce no symptoms in the early stages, and most can be prevented or minimized with a combination of regular medical care and blood glucose monitoring.
CONTROLLING BLOOD SUGAR — The long-term complications of diabetes result from the effects of hyperglycemia (elevated blood glucose levels) on blood vessels. Two important studies, the Diabetes Control and Complications Trial (DCCT) in patients with type 1 diabetes and the United Kingdom Prospective Diabetes Study (UKPDS) in patients with type 2 diabetes, found that patients with lower blood glucose values had fewer complications than those with higher values.
Thus, keeping blood sugars close to normal can help prevent the long-term complications of diabetes mellitus. However, there are some risks associated with tight control, particularly an increased risk of hypoglycemia (low blood sugar).
Monitoring blood sugar levels — Monitoring blood sugars with finger sticks at home can indicate how well diabetes is controlled and serves as a guide to adjusting therapy. (See "Patient information: Self-blood glucose monitoring"). For most patients, a target for fasting blood glucose and for blood glucose levels before each meal is 80-120 mg/dl (4.4 to 6.6 mmol/L); however, these targets may need to be individualized for a patient by their doctor or health care team.
A blood test called A1C is also used to monitor blood sugar control; the result provides an average of blood glucose levels during the previous one to three months. An A1C of 7 percent or less is recommended; this corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show figure 1). The target may be somewhat higher in people who are older or who have other conditions that increase the risks associated with hypoglycemia. Patients who are unable to reach this goal can be reassured that even small decreases in A1C lowers the risk of diabetes-related complications to some degree.
The combination of A1C and fingerstick blood sugars provides information about the average blood sugar as well as daily fluctuations in blood sugar.
Type 1 diabetes — Blood sugar control in type 1 diabetes requires some form of insulin, which can be given with insulin injections, an insulin pump, or a combination of inhaled insulin and insulin injections. Most healthcare providers recommend intensive insulin therapy, which requires frequent injections, inhaled insulin, or use of an insulin pump and blood glucose monitoring. (See "Patient information: Diabetes type 1: Insulin treatment").
Intensive insulin therapy increases the risk of low blood glucose, is more expensive than traditional insulin therapy, and requires that patients monitor their blood glucose levels, dietary intake and activities; the severity of diabetic complications or hypoglycemia may limit this form of therapy in some patients with type 1 diabetes. Patients can experience weight gain with intensive insulin therapy; regular exercise and monitoring dietary intake can prevent weight gain. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Type 2 diabetes — Blood glucose control in type 2 diabetes may be possible with lifestyle changes alone or in combination with oral medications. Insulin is necessary in some cases in early treatment; many patients who do not initially require insulin may do so over time as their ability to manufacture insulin decreases. Generally the insulin regimen for type 2 requires fewer injections and less intensive monitoring than for type 1, although intensive insulin therapy may be recommended for some patients (See "Patient information: Diabetes type 2: Insulin treatment").
EYE COMPLICATIONS — Regular eye examinations are essential for detecting eye complications (called retinopathy) at an early stage, when they can be monitored and treated to preserve vision. This examination should be performed by a doctor who specializes in the eyes (called an ophthalmologist or optometrist). An eye exam should include dilating the pupils (with medicated eye drops) in order to completely visualize the retina. Unless the pupils are medicated, they contract in response to light, making it impossible to view the entire retina.
In some patients with retinopathy, photographs of the retina will be taken to monitor and better visualize the changes. The risk of diabetic retinopathy varies with the type and duration of diabetes and with other life events. Thus, the screening guidelines differ from one person to another.
Type 1 diabetes — People with type 1 diabetes should have an eye examination by an ophthalmologist or optometrist beginning five years after they are diagnosed with diabetes, although screening is usually not necessary before puberty. Patients who have difficulty with their vision or who require glasses or contacts may need to be seen sooner. The frequency of subsequent examinations will depend upon the results of the initial exam. Doctors usually recommend eye exams every one to two years after the initial examination.
Type 2 diabetes — People with type 2 diabetes should have an eye examination by an ophthalmologist or optometrist when they are first diagnosed with diabetes. The frequency of subsequent exams will depend upon the results of the initial examination. Doctors usually recommend eye exams every one to two years after the initial examination.
FOOT CARE — Diabetes can decrease the blood supply to the foot and damage the nerves that carry sensation. These changes put the feet at risk for potentially serious complications such as foot ulcers. Foot complications are very common among people with diabetes, and may be unnoticed until the condition is severe. (See "Patient information: Foot care in diabetes").
Self exam — Patients with diabetes should examine their feet for changes every day. It is important to examine all parts of the feet, especially the area between the toes. Patients should look for broken skin, ulcers, blisters, areas of increased warmth or redness, or changes in callus formation; a healthcare provider should be notified if any of these changes are found.
Patients should include a self-examination in their daily bathing or dressing routine. It may be necessary to use a mirror to see the bottoms of the feet clearly. Patients who are unable to reach their feet or see them completely, even with the help of a mirror, should have someone else (such as a spouse or other family member) assist with the examination.
Clinical exam — During a routine medical visit, the clinician will check the blood flow and sensation in the feet. In people with type 1 diabetes, annual foot examinations should begin five years after diagnosis. In people with type 2 diabetes, annual foot exams should begin at the time of diagnosis.
During a foot examination, the clinician will look for changes such as ulcers, cold feet, thin skin, bluish skin color, and skin breaks associated with athlete's foot. The clinician will also test the sensation in the feet to determine if it is normal or diminished. Patients with decreased sensation are at risk for foot injuries that are unnoticed due to lack of pain.
KIDNEY COMPLICATIONS — Diabetes can alter the normal function of the kidneys. A urine test which measures the amount of protein (albumin) in the urine can alert a healthcare provider that diabetes is affecting the kidney's filtering action. Microscopic amounts of albumin in the urine (microalbuminuria) can be an early indicator of diabetes-related kidney complications (called nephropathy). The amount of albumin in the urine can also help the provider determine if nephropathy is worsening. (See "Patient information: Protein in the urine (proteinuria)").
Urine screening tests should begin in people with type 1 diabetes about five years after diagnosis, and in people with type 2 diabetes at the time of diagnosis. If the test shows that there is protein in the urine, tight blood glucose and lipid control are recommended; a medication may be recommended if albuminuria does not improve.
A blood pressure medication (an ACE inhibitor or angiotension receptor blocker [ARB]) is generally recommended for patients with albuminuria that does not improve, even if blood pressures are normal. Patients with elevated blood pressures and albuminuria are also treated with an ACE inhibitor or ARB. These medications decrease the amount of protein in the urine and can prevent or slow the progression of diabetes-related kidney disease.
HYPERTENSION AND RELATED COMPLICATIONS — Many people with diabetes have hypertension (high blood pressure). Although high blood pressure produces few symptoms, it has two negative effects: it stresses the cardiovascular system and increases the progression of diabetic complications of the kidney and eye. A healthcare provider can diagnose high blood pressure by measuring blood pressure on a regular basis. (See "Patient information: High blood pressure overview").
A blood pressure reading below 130/80 is an ideal goal for most people with diabetes who do not have kidney complications; a lower blood pressure goal (<120/75) may be recommended for people with diabetes who have kidney complications.
If a patient is diagnosed with prehypertension (>120/80), the healthcare provider may recommend weight loss, exercise, decreasing the amount of salt in the diet, quitting smoking, and decreasing alcohol intake. These measures can sometimes reduce blood pressure to normal. (See "Patient information: High blood pressure, diet and weight").
If these measures are not effective or the blood pressure must be lowered quickly, the provider will likely recommend one of several high blood pressure medications. The provider can discuss the pros and cons of each medication and the goals of treatment (See "Patient information: High blood pressure treatment").
HEART COMPLICATIONS — In addition to lowering blood glucose levels, a number of other measures are important to reduce the risk of cardiac disease. Quit smoking Manage high blood pressure with lifestyle modifications and/or medication(s) Patients should have a fasting lipid blood test to measure cholesterol and triglycerides, and modify their diets. some patients may need medication to lower their LDL ("bad cholesterol") or trigylcerides, if they are high.
If medication is needed, a statin drug should be included whenever possible. The statin drugs have been shown to decrease the future risk of heart attacks, strokes, and death in people with diabetes who are over age 40, even when cholesterol levels are normal. The American Diabetes Association recommends that patients with diabetes have a low density lipoprotein (LDL) cholesterol level less than 100 mg/dL. Some studies suggest lowering LDL to 70 to 80 mg/dL. (See "Patient information: High cholesterol and lipids (hyperlipidemia)"). Aspirin (81 to 162 mg per day) is recommended for all persons with diabetes over the age of 40 years. (See "Patient information: Aspirin and heart disease").
PREGNANCY AND DIABETES — Control of diabetes and its potential complications is especially important in women planning to become pregnant, as well as in those who already are pregnant. Controlling blood glucose levels before and during pregnancy decreases the risk of a number of complications in both the mother and the baby. A separate topic review is available on this subject. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Pregnancy can cause a worsening of diabetic retinopathy. Thus, women with type 1 or 2 diabetes who become pregnant should have an eye examination by an ophthalmologist or optometrist during the first trimester (three months) of their pregnancy. The frequency of subsequent eye exams during pregnancy will depend upon the results of the initial examination. In most cases, doctors recommend eye exams every three months until delivery.
These guidelines do not apply to women who have gestational diabetes -- a form of diabetes that develops during pregnancy and usually resolves after delivery. These women are not at risk for diabetic retinopathy.
THE IMPORTANCE OF REGULAR MEDICAL CARE — Regular medical care is critical to long-term health for people with diabetes, particularly when it comes to preventing, detecting, and slowing the progression of complications. A healthcare provider can recommend a regular schedule for visits, screening, and monitoring tests based upon a patient's type of diabetes (1 or 2), the duration of the disease, the presence of any complications, and the presence of other underlying medical problems.
In addition to diabetes care, patients also need to be sure they have regular screening for other health problems. For women, this may includes a cervical cancer screening, mammogram and clinical breast exam, and bone density testing. For men, prostate cancer screening is recommended after age 40. For both men and women, colon cancer screening is recommended after age 50. (See "Patient information: Screening for cervical cancer" and see "Patient information: Screening for breast cancer" and see "Patient information: Osteoporosis causes; diagnosis; and screening"). and see "Patient information: Prostate cancer screening" and see "Patient information: Screening for colon cancer").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
[1-6]
Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 1993; 329:977.
2. Effect of intensive diabetes management on macrovascular events and risk factors in the Diabetes Control and Complications Trial. Am J Cardiol 1995; 75:894.
3. Abraira, C, Colwell, JA, Nuttall, FQ, et al. Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type II Diabetes (VACSDM): Results of a feasibility trial. Diabetes Care 1995; 18:1113.
4. Nathan, DM, Cleary, PA, Backlund, JY, et al. Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. N Engl J Med 2005; 353:2643.
5. Sustained effect of intensive treatment of type 1 diabetes mellitus on development and progression of diabetic nephropathy: the Epidemiology of Diabetes Interventions and Complications (EDIC) study. JAMA 2003; 290:2159.
6. Gray, A, Raikou, M, McGuire, A, et al. Cost effectiveness of an intensive blood glucose control policy in patients with type 2 diabetes: economic analysis alongside randomised controlled trial (UKPDS 41). United Kingdom Prospective Diabetes Study Group. BMJ 2000; 320:1373
Many of these complications produce no symptoms in the early stages, and most can be prevented or minimized with a combination of regular medical care and blood glucose monitoring.
CONTROLLING BLOOD SUGAR — The long-term complications of diabetes result from the effects of hyperglycemia (elevated blood glucose levels) on blood vessels. Two important studies, the Diabetes Control and Complications Trial (DCCT) in patients with type 1 diabetes and the United Kingdom Prospective Diabetes Study (UKPDS) in patients with type 2 diabetes, found that patients with lower blood glucose values had fewer complications than those with higher values.
Thus, keeping blood sugars close to normal can help prevent the long-term complications of diabetes mellitus. However, there are some risks associated with tight control, particularly an increased risk of hypoglycemia (low blood sugar).
Monitoring blood sugar levels — Monitoring blood sugars with finger sticks at home can indicate how well diabetes is controlled and serves as a guide to adjusting therapy. (See "Patient information: Self-blood glucose monitoring"). For most patients, a target for fasting blood glucose and for blood glucose levels before each meal is 80-120 mg/dl (4.4 to 6.6 mmol/L); however, these targets may need to be individualized for a patient by their doctor or health care team.
A blood test called A1C is also used to monitor blood sugar control; the result provides an average of blood glucose levels during the previous one to three months. An A1C of 7 percent or less is recommended; this corresponds to an average blood glucose of 150 mg/dL (8.3 mmol/L, show figure 1). The target may be somewhat higher in people who are older or who have other conditions that increase the risks associated with hypoglycemia. Patients who are unable to reach this goal can be reassured that even small decreases in A1C lowers the risk of diabetes-related complications to some degree.
The combination of A1C and fingerstick blood sugars provides information about the average blood sugar as well as daily fluctuations in blood sugar.
Type 1 diabetes — Blood sugar control in type 1 diabetes requires some form of insulin, which can be given with insulin injections, an insulin pump, or a combination of inhaled insulin and insulin injections. Most healthcare providers recommend intensive insulin therapy, which requires frequent injections, inhaled insulin, or use of an insulin pump and blood glucose monitoring. (See "Patient information: Diabetes type 1: Insulin treatment").
Intensive insulin therapy increases the risk of low blood glucose, is more expensive than traditional insulin therapy, and requires that patients monitor their blood glucose levels, dietary intake and activities; the severity of diabetic complications or hypoglycemia may limit this form of therapy in some patients with type 1 diabetes. Patients can experience weight gain with intensive insulin therapy; regular exercise and monitoring dietary intake can prevent weight gain. (See "Patient information: Hypoglycemia (low blood glucose) in diabetes").
Type 2 diabetes — Blood glucose control in type 2 diabetes may be possible with lifestyle changes alone or in combination with oral medications. Insulin is necessary in some cases in early treatment; many patients who do not initially require insulin may do so over time as their ability to manufacture insulin decreases. Generally the insulin regimen for type 2 requires fewer injections and less intensive monitoring than for type 1, although intensive insulin therapy may be recommended for some patients (See "Patient information: Diabetes type 2: Insulin treatment").
EYE COMPLICATIONS — Regular eye examinations are essential for detecting eye complications (called retinopathy) at an early stage, when they can be monitored and treated to preserve vision. This examination should be performed by a doctor who specializes in the eyes (called an ophthalmologist or optometrist). An eye exam should include dilating the pupils (with medicated eye drops) in order to completely visualize the retina. Unless the pupils are medicated, they contract in response to light, making it impossible to view the entire retina.
In some patients with retinopathy, photographs of the retina will be taken to monitor and better visualize the changes. The risk of diabetic retinopathy varies with the type and duration of diabetes and with other life events. Thus, the screening guidelines differ from one person to another.
Type 1 diabetes — People with type 1 diabetes should have an eye examination by an ophthalmologist or optometrist beginning five years after they are diagnosed with diabetes, although screening is usually not necessary before puberty. Patients who have difficulty with their vision or who require glasses or contacts may need to be seen sooner. The frequency of subsequent examinations will depend upon the results of the initial exam. Doctors usually recommend eye exams every one to two years after the initial examination.
Type 2 diabetes — People with type 2 diabetes should have an eye examination by an ophthalmologist or optometrist when they are first diagnosed with diabetes. The frequency of subsequent exams will depend upon the results of the initial examination. Doctors usually recommend eye exams every one to two years after the initial examination.
FOOT CARE — Diabetes can decrease the blood supply to the foot and damage the nerves that carry sensation. These changes put the feet at risk for potentially serious complications such as foot ulcers. Foot complications are very common among people with diabetes, and may be unnoticed until the condition is severe. (See "Patient information: Foot care in diabetes").
Self exam — Patients with diabetes should examine their feet for changes every day. It is important to examine all parts of the feet, especially the area between the toes. Patients should look for broken skin, ulcers, blisters, areas of increased warmth or redness, or changes in callus formation; a healthcare provider should be notified if any of these changes are found.
Patients should include a self-examination in their daily bathing or dressing routine. It may be necessary to use a mirror to see the bottoms of the feet clearly. Patients who are unable to reach their feet or see them completely, even with the help of a mirror, should have someone else (such as a spouse or other family member) assist with the examination.
Clinical exam — During a routine medical visit, the clinician will check the blood flow and sensation in the feet. In people with type 1 diabetes, annual foot examinations should begin five years after diagnosis. In people with type 2 diabetes, annual foot exams should begin at the time of diagnosis.
During a foot examination, the clinician will look for changes such as ulcers, cold feet, thin skin, bluish skin color, and skin breaks associated with athlete's foot. The clinician will also test the sensation in the feet to determine if it is normal or diminished. Patients with decreased sensation are at risk for foot injuries that are unnoticed due to lack of pain.
KIDNEY COMPLICATIONS — Diabetes can alter the normal function of the kidneys. A urine test which measures the amount of protein (albumin) in the urine can alert a healthcare provider that diabetes is affecting the kidney's filtering action. Microscopic amounts of albumin in the urine (microalbuminuria) can be an early indicator of diabetes-related kidney complications (called nephropathy). The amount of albumin in the urine can also help the provider determine if nephropathy is worsening. (See "Patient information: Protein in the urine (proteinuria)").
Urine screening tests should begin in people with type 1 diabetes about five years after diagnosis, and in people with type 2 diabetes at the time of diagnosis. If the test shows that there is protein in the urine, tight blood glucose and lipid control are recommended; a medication may be recommended if albuminuria does not improve.
A blood pressure medication (an ACE inhibitor or angiotension receptor blocker [ARB]) is generally recommended for patients with albuminuria that does not improve, even if blood pressures are normal. Patients with elevated blood pressures and albuminuria are also treated with an ACE inhibitor or ARB. These medications decrease the amount of protein in the urine and can prevent or slow the progression of diabetes-related kidney disease.
HYPERTENSION AND RELATED COMPLICATIONS — Many people with diabetes have hypertension (high blood pressure). Although high blood pressure produces few symptoms, it has two negative effects: it stresses the cardiovascular system and increases the progression of diabetic complications of the kidney and eye. A healthcare provider can diagnose high blood pressure by measuring blood pressure on a regular basis. (See "Patient information: High blood pressure overview").
A blood pressure reading below 130/80 is an ideal goal for most people with diabetes who do not have kidney complications; a lower blood pressure goal (<120/75) may be recommended for people with diabetes who have kidney complications.
If a patient is diagnosed with prehypertension (>120/80), the healthcare provider may recommend weight loss, exercise, decreasing the amount of salt in the diet, quitting smoking, and decreasing alcohol intake. These measures can sometimes reduce blood pressure to normal. (See "Patient information: High blood pressure, diet and weight").
If these measures are not effective or the blood pressure must be lowered quickly, the provider will likely recommend one of several high blood pressure medications. The provider can discuss the pros and cons of each medication and the goals of treatment (See "Patient information: High blood pressure treatment").
HEART COMPLICATIONS — In addition to lowering blood glucose levels, a number of other measures are important to reduce the risk of cardiac disease. Quit smoking Manage high blood pressure with lifestyle modifications and/or medication(s) Patients should have a fasting lipid blood test to measure cholesterol and triglycerides, and modify their diets. some patients may need medication to lower their LDL ("bad cholesterol") or trigylcerides, if they are high.
If medication is needed, a statin drug should be included whenever possible. The statin drugs have been shown to decrease the future risk of heart attacks, strokes, and death in people with diabetes who are over age 40, even when cholesterol levels are normal. The American Diabetes Association recommends that patients with diabetes have a low density lipoprotein (LDL) cholesterol level less than 100 mg/dL. Some studies suggest lowering LDL to 70 to 80 mg/dL. (See "Patient information: High cholesterol and lipids (hyperlipidemia)"). Aspirin (81 to 162 mg per day) is recommended for all persons with diabetes over the age of 40 years. (See "Patient information: Aspirin and heart disease").
PREGNANCY AND DIABETES — Control of diabetes and its potential complications is especially important in women planning to become pregnant, as well as in those who already are pregnant. Controlling blood glucose levels before and during pregnancy decreases the risk of a number of complications in both the mother and the baby. A separate topic review is available on this subject. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes").
Pregnancy can cause a worsening of diabetic retinopathy. Thus, women with type 1 or 2 diabetes who become pregnant should have an eye examination by an ophthalmologist or optometrist during the first trimester (three months) of their pregnancy. The frequency of subsequent eye exams during pregnancy will depend upon the results of the initial examination. In most cases, doctors recommend eye exams every three months until delivery.
These guidelines do not apply to women who have gestational diabetes -- a form of diabetes that develops during pregnancy and usually resolves after delivery. These women are not at risk for diabetic retinopathy.
THE IMPORTANCE OF REGULAR MEDICAL CARE — Regular medical care is critical to long-term health for people with diabetes, particularly when it comes to preventing, detecting, and slowing the progression of complications. A healthcare provider can recommend a regular schedule for visits, screening, and monitoring tests based upon a patient's type of diabetes (1 or 2), the duration of the disease, the presence of any complications, and the presence of other underlying medical problems.
In addition to diabetes care, patients also need to be sure they have regular screening for other health problems. For women, this may includes a cervical cancer screening, mammogram and clinical breast exam, and bone density testing. For men, prostate cancer screening is recommended after age 40. For both men and women, colon cancer screening is recommended after age 50. (See "Patient information: Screening for cervical cancer" and see "Patient information: Screening for breast cancer" and see "Patient information: Osteoporosis causes; diagnosis; and screening"). and see "Patient information: Prostate cancer screening" and see "Patient information: Screening for colon cancer").
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
National Institute of Diabetes and Digestive and Kidney Diseases
(www.niddk.nih.gov/)
American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
(www.diabetes.org)
The Hormone Foundation
(www.hormone.org/public/diabetes.cfm, available in English and Spanish)
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2. Effect of intensive diabetes management on macrovascular events and risk factors in the Diabetes Control and Complications Trial. Am J Cardiol 1995; 75:894.
3. Abraira, C, Colwell, JA, Nuttall, FQ, et al. Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type II Diabetes (VACSDM): Results of a feasibility trial. Diabetes Care 1995; 18:1113.
4. Nathan, DM, Cleary, PA, Backlund, JY, et al. Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. N Engl J Med 2005; 353:2643.
5. Sustained effect of intensive treatment of type 1 diabetes mellitus on development and progression of diabetic nephropathy: the Epidemiology of Diabetes Interventions and Complications (EDIC) study. JAMA 2003; 290:2159.
6. Gray, A, Raikou, M, McGuire, A, et al. Cost effectiveness of an intensive blood glucose control policy in patients with type 2 diabetes: economic analysis alongside randomised controlled trial (UKPDS 41). United Kingdom Prospective Diabetes Study Group. BMJ 2000; 320:1373
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