By Amy Adams, MS

Reviewed By Jeremy Walston, MD
Last Updated September 15, 2000

Diabetes mellitus is a disease in which high levels of glucose (a type of sugar) accumulate in the blood — a condition called hyperglycemia. Diabetes mellitus should not be confused with a much rarer form of diabetes, called diabetes insipidus, which is caused by an imbalance in hormones that regulate the kidney. We will use the term "diabetes" to refer specifically to diabetes mellitus.

Who Gets Diabetes?

Diabetes affects six percent of all people in the United States and is one of the most common chronic diseases in children and adults. Of the 16 million people affected, roughly a third do not know that they have the disease.

In 1996, diabetes was the seventh leading cause of death in the United States. However, that number is considered an underestimate by many experts because in some cases, the long-term effects of diabetes such as heart attack or kidney failure may be listed as the cause of death, rather than the underlying diabetes.

People with diabetes in their family are at higher risk for developing diabetes than those with no family history, as are people in certain ethnic groups such as people of African, Hispanic, Native American, or Pacific Island descent. Diabetes is equally likely to occur in males and females.

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The Role of Insulin in Diabetes

After you eat a meal, your body breaks food down into a sugar called glucose. In most people, insulin in the bloodstream helps cells take up glucose and use it as fuel. Glucose levels increase after a meal, but quickly return to normal as cells remove excess glucose from the bloodstream.

This normal process of using glucose for energy falls apart in diabetes. In a diabetic person, either the pancreas cells do not make insulin or cells of the body can not use the insulin properly. Without insulin, cells are unable to take up glucose. Instead, glucose builds up in the bloodstream where it can cause damage to eyes, nerves, and blood vessels, as well as cause a person to feel thirsty or urinate frequently.

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Types of Diabetes

Over the years, physicians and researchers have come to understand that diabetes is not just one disease, but several diseases that result in high blood sugar levels. Because of differences in disease origins, symptoms, and screening and treatment strategies, the medical community has divided diabetes into several major categories.

• Type 1 diabetes occurs when the immune system destroys the pancreas cells that produce insulin (beta cells). Because Type 1 diabetics produce no insulin, they must receive regular insulin injections in order to control their blood sugar level. This type of diabetes generally develops during childhood or puberty, but can occur at any age. Type 1 diabetes was once called child onset diabetes or Insulin Dependent Diabetes Mellitus (IDDM).

More on Type 1 Diabetes

• Type 2 diabetes occurs when muscle and fat cells are unable to use insulin properly — also referred to as insulin resistance. While some people who have Type 2 diabetes need to take insulin to control their blood sugar level, many others can keep their blood sugar at an acceptable level by modifying their diet, getting regular exercise, or taking medication that helps their body use insulin more effectively. Type 2 diabetes usually affects adults older than 45 years, though it can occur in adolescents. Type 2 diabetes was once called adult onset diabetes or Non-Insulin Dependent Diabetes Mellitus (NIDDM).

More on Type 2 Diabetes

 

• Gestational diabetes is a form of diabetes that only occurs during a pregnancy. It effects about four percent of all pregnancies, but generally symptoms disappear within six weeks of delivery. Like Type 2 diabetes, gestational diabetes does not result from a lack of insulin, but from the body's inability to use the insulin properly. In fact, pregnant women usually have more insulin in their blood than women who are not pregnant. However, the placenta (which supplies the fetus with nutrients and water from the mother's blood) makes a number of hormones that have a blocking effect on insulin. In most women, the pancreas is able to produce enough insulin to compensate for this effect. When it can't, gestational diabetes results. Gestational diabetes poses a number of risks to both mother and child, but generally these can be controlled by keeping blood sugar levels as close to normal as possible during the pregnancy — either through diet and exercise, oral medications, or, in some cases, through insulin injections. Gestational diabetes occurs more frequently in women who have a family history of Type 2 diabetes and puts women at a higher risk for developing Type 2 diabetes later in life. (For news about gestational diabetes, see Related News below.)
  
  
• Other forms of diabetes occur as part of related disorders that include diabetes as one of their symptoms. These disorders — which make up less than two percent of diabetes cases — include defects of the pancreas cells, defects in insulin action, diseases of the pancreas and kidneys, drug or chemical interactions with the body, infections, and other genetic syndromes such as hemochromatosis.

More on Hemochromatosis

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The Consequences of Diabetes

Signs and Symptoms

Symptoms of Diabetes: Thirst Frequent urination Sudden weight loss Blurred vision Fatigue Irritability

If a person has any signs of diabetes, a doctor should test their body's ability to use glucose with a fasting glucose test or a glucose tolerance test. Both of these tests can tell a doctor whether there are unusually high levels of glucose in the blood. Because some people may not notice symptoms of diabetes until after cells have become damaged (particularly in Type 2 diabetes), it is important for people with diabetes in the their families to have their blood glucose levels tested regularly.

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There are a number of factors, both genetic and environmental, that may increase a person's risk of developing diabetes.

People who have family members with diabetes are at a higher risk for developing the disease. For both Type 1 and Type 2 diabetes, researchers have found alterations (mutations) in many different genes that appear to put people at risk for developing the diabetes. Some mutations increase a person's risk only slightly, while others put people at a much higher risk.

Although diabetes can run in families, inheriting a particular gene mutation does not guarantee that a person will get the disease. They must also have certain environmental factors that trigger diabetes. These differ in Type 1 and Type 2 but they can include obesity, inactivity, increasing age, and a history of gestational diabetes.

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Screening

Treatment

Treatment for diabetes varies depending on the type and severity of diabetes. Treatments may include:

• Diet: A diet that is low in sugar and high in complex carbohydrates such as beans, vegetables, and grains prevents high glucose levels in the blood, and minimizes the need for insulin. Although people with both Type 1 and Type 2 diabetes need to watch their diet carefully, only Type 2 diabetics can use diet alone to control the disease.
• Exercise: Regular moderate exercise helps the body use glucose more effectively. However, people with diabetes should consult their doctors before beginning an exercise program.
• Oral medications: There are many medications available that help diabetics use their body's insulin more effectively. These medications are only effective for Type 2 diabetics who produce some insulin.
• Insulin injections: In Type 1 diabetes, or more severe forms of Type 2 diabetes, insulin injections are needed in order to keep the blood glucose level under control.

The goal of any diabetes treatment plan is to keep blood sugar levels as close to normal as possible. People who do manage to keep their blood sugar levels under control can lead long healthy lives. However, managing diabetes can be time-consuming for the person with diabetes and their family. For detailed information about managing diabetes, we recommend that you visit the American Diabetes Association or the Canadian Diabetes Association.

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Related News

In order to view these articles you will need to have a MyGeneticHealth account. If you are not already a member, selecting the article will automatically take you to a page where you can sign up. Maternal weight before pregnancy is predictive of recurrent gestational diabetes Inhaled insulin may help limit injections in diabetics Researchers develop dual glucose-insulin sensor

References

National Institute of Diabetes and Digestion and Kidney Diseases (1999). Diabetes Statistics. Bethesda, MD: National Institutes of Health. Publication No. 99-3892.

American Diabetes Association (1999). Clinical Practice Recommendations 1999. Diabetes Care (Suppl. 1), 22, S1-S114.

Harris, M., (1999). Classification, Diagnostic Criteria, and Screening for Diabetes. In Diabetes in America. Bethesda, MD: National Institute of Diabetes and Digestion and Kidney Diseases, National Institute of Health.