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What is Diabetes?

Diabetes is a chronic disease in which the body has trouble regulating blood sugar. The two most common types of diabetes are type 1 and type 2. Both forms result from the body's inability to either produce or use insulin. A third type, gestational diabetes, occurs only during pregnancy and may lead to type 2 diabetes.

Insulin is the hormone that controls the movement of glucose from the blood into cells. The pancreas produces insulin. Glucose — also called blood sugar — constantly moves through the bloodstream to supply the body cells with the energy needed for muscle contractions and metabolism.

The job of insulin is to make sure the glucose actually moves into the body's cells. Without insulin, the glucose builds up in the bloodstream. Over time, elevated glucose levels can damage the linings of blood vessels, leading to damage to the eyes, kidneys, and other sensitive tissues. This vascular damage can cause blindness (diabetic retinopathy), impotence, kidney failure (diabetic nephropathy and end-stage renal disease, which may require dialysis and/or kidney transplantation), increased risk for heart attack, and the deterioration of nerves or blood vessels. It also can cause poor blood flow to the arms and legs, resulting in poor wound healing and possible amputation. Diabetes is the leading cause of new blindness in adults. It is also the most common condition leading to dialysis and kidney transplants, and the most common reason for below-the-knee amputations, other than injuries.

Type 1 diabetes is caused when the cells in the pancreas (called beta islet cells) that produce insulin are destroyed, leading to absolute insulin deficiency. Although type 1 diabetes can occur at any age, it is usually diagnosed in children and young adults. Genetic, autoimmune, and environmental factors are considered risk factors for type 1 diabetes. Currently, there is no known way to prevent type 1 diabetes.

Type 2 diabetes affects about nine out of 10 people with diabetes. It is the most common form of diabetes. In type 2 diabetes, the pancreas either does not produce enough insulin, or the body becomes less and less efficient at getting insulin to move glucose into the cells (insulin resistance). A person is resistant to insulin and usually has relative (rather than absolute) insulin deficiency. You can inherit the potential for type 2 diabetes, but whether you actually develop it may depend on a number of factors, such as poor eating habits, lack of exercise, and weight gain. Other risk factors include older age and history of gestational diabetes. Race and ethnicity can also influence the occurrence of type 2 diabetes. African-Americans, Hispanic Americans, American Indians, and Native Hawaiians are at a particularly high risk of developing type 2 diabetes and its complications.