Diabetes is a lifelong (chronic) disease in which there are high levels of sugar in the blood.
Causes, incidence, and risk factors
Insulin is a hormone produced by the pancreas to control blood sugar. Diabetes can be caused by too little insulin, resistance to insulin, or both.
To understand diabetes, it is important to first understand the normal process by which food is broken down and used by the body for energy. Several things happen when food is digested:
- A sugar called glucose enters the bloodstream. Glucose is a source of fuel for the body.
- An organ called the pancreas makes insulin. The role of insulin is to move glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel.
People with diabetes have high blood sugar because their body cannot move sugar into fat, liver, and muscle cells to be stored for energy. This is because either:
- Their pancreas does not make enough insulin
- Their cells do not respond to insulin normally
- Both of the above
There are three major types of diabetes. The causes and risk factors are different for each type:
- Type 1 diabetes can occur at any age, but it is most often diagnosed in children, teens, or young adults. In this disease, the body makes little or no insulin. Daily injections of insulin are needed. The exact cause is unknown.
- Type 2 diabetes makes up most of diabetes cases. It most often occurs in adulthood, but teens and young adults are now being diagnosed with it because of high obesity rates. Many people with type 2 diabetes do not know they have it.
- Gestational diabetes is high blood sugar that develops at any time during pregnancy in a woman who does not have diabetes.
Diabetes affects more than 20 million Americans. Over 40 million Americans have pre-diabetes (early type 2 diabetes).
High blood sugar levels can cause several symptoms, including:
- Blurry vision
- Excess thirst
- Frequent urination
- Weight loss
Because type 2 diabetes develops slowly, some people with high blood sugar have no symptoms.
Symptoms of type 1 diabetes develop over a short period of time. People may be very sick by the time they are diagnosed.
Signs and tests
A urine analysis may be used to look for high blood sugar. However, a urine test alone does not diagnose diabetes.
Your health care provider may suspect that you have diabetes if your blood sugar level is higher than 200 mg/dL. To confirm the diagnosis, one or more of the following tests must be done.
- Fasting blood glucose level -- diabetes is diagnosed if it is higher than 126 mg/dL twice. Levels between 100 and 126 mg/dL are called impaired fasting glucose or pre-diabetes. These levels are risk factors for type 2 diabetes.
- Hemoglobin A1c test --
- Normal: Less than 5.7%
- Pre-diabetes: 5.7% - 6.4%
- Diabetes: 6.5% or higher
- Oral glucose tolerance test -- diabetes is diagnosed if glucose level is higher than 200 mg/dL after 2 hours. (This test is used more often for type 2 diabetes.)
Screening for type 2 diabetes in people who have no symptoms is recommended for:
- Overweight children who have other risk factors for diabetes, starting at age 10 and repeated every 2 years
- Overweight adults (BMI greater than 25) who have other risk factors
- Adults over age 45, repeated every 3 years
There is no cure for diabetes. Treatment involves medicines, diet, and exercise to control blood sugar and prevent symptoms and problems.
For more information on how to take care of your diabetes, see also:
For more information, see diabetes resources.
Studies have shown that better control of blood sugar, cholesterol, and blood pressure levels in persons with diabetes helps reduce the risk of kidney disease, eye disease, nervous system disease, heart attack, and stroke.
Emergency complications include:
- Diabetic hyperglycemic hyperosmolar coma
- Diabetic ketoacidosis
After many years, diabetes can lead to other serious problems:
- You could have eye problems, including trouble seeing (especially at night) and light sensitivity. You could become blind.
- Your feet and skin can develop sores and infections. After a long time, your foot or leg may need to be removed. Infection can also cause pain and itching in other parts of the body.
- Diabetes may make it harder to control your blood pressure and cholesterol. This can lead to a heart attack, stroke, or other problems. It can become harder for blood to flow to your legs and feet.
- Nerves in the body can become damaged, causing pain, tingling, and a loss of feeling.
- Because of nerve damage, you could have problems digesting the food you eat. You could feel weakness or have trouble going to the bathroom. Nerve damage can also make it harder for men to have an erection.
- High blood sugar and other problems can lead to kidney damage. The kidneys might not work as well, and they may even stop working.
Keeping an ideal body weight and an active lifestyle may prevent type 2 diabetes.
There is no way to prevent type 1 diabetes.
To prevent complications of diabetes, visit your health care provider or diabetes educator at least four times a year. Talk about any problems you are having.
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American Diabetes Association. Standards of medical care in diabetes -- 2011. Diabetes Care. 2010; 34 Suppl 1:S11-S61.
Pignone M, Alberts MJ, Colwell JA, Cushman M, Inzucchi SE, Mukherjee D, et al. Aspirin for primary prevention of cardiovascular events in people with diabetes: a position statement of the American Diabetes Association, a scientific statement of the American Heart Association, and an expert consensus document of the American College of Cardiology Foundation. Circulation. 2010;121:2694-2701.
Eisenbarth GS, Polonsky KS, Buse JB. Type 1 Diabetes Mellitus. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Kronenberg: Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 31.
Reviewed By: A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Ari S. Eckman, MD, Chief, Division of Endocrinology, Diabetes, and Metabolism, Trinitas Regional Medical Center, Elizabeth, NJ. Review provided by VeriMed Healthcare Network (6/28/2011).