A disease that occurs when the body is not able to use sugar as it should. The body needs sugar for growth and energy for daily activities. It gets sugar when it changes food into glucose (a form of sugar). A hormone called insulin is needed for the glucose to be taken up and used by the body. Diabetes occurs when the body cannot make use of the glucose in the blood for energy because either the pancreas is not able to make enough insulin or the insulin that is available is not effective. The beta cells in areas of the pancreas called the islets of Langerhans usually make insulin.

There are two main types of diabetes mellitus: Type 1 and Type 2. In Type 1 diabetes, the pancreas makes little or no insulin because the insulin-producing beta cells have been destroyed. This type usually appears suddenly and most commonly in younger people under age 30. Treatment consists of daily insulin injections or use of an insulin pump, a planned diet and regular exercise, and daily self-monitoring of blood glucose.

In Type 2, the pancreas makes some insulin, sometimes too much. The insulin, however, is not effective (see Insulin Resistance). Type 2 is controlled by diet and exercise and daily monitoring of glucose levels. Sometimes oral drugs that lower blood glucose levels or insulin injections are needed. This type of diabetes usually develops gradually, most often in people over 40 years of age. Type 2 accounts for 90 to 95 percent of diabetes.

Signs and symptoms of diabetes may include having to urinate often, losing weight, getting very thirsty, and being hungry all the time. Other signs are blurred vision, itchy skin, and slow healing of sores.

In Type 1, if the level of insulin is too low for a long period of time, the body begins to break down its stores of fat for energy. This causes the body to release acids (ketones) into the blood. The result is called ketoacidosis, a severe condition that may put a person into a coma if not treated right away.

The causes of diabetes are not known. Scientists think that Type 1 diabetes may be more than one disease and may have many causes. They are looking at hereditary (whether or not the person has parents or other family members with the disease) and at factors both inside and outside the body, including viruses.

Type 2 diabetes appears to be closely associated with obesity and with the body resisting the action of insulin.