ADA Definition

Diabetes is a disease in which the body does not produce or properly use insulin. Insulin is a hormone that is needed to convert sugar, starches and other food into energy needed for daily life. The cause of diabetes continues to be a mystery, although both genetics and environmental factors such as obesity and lack of exercise appear to play roles.
Approximately 17 million people in the United States, or 6.2% of the population, have diabetes. While an estimated 11.1 million have been diagnosed, unfortunately, 5.9 million people (or one-third) are unaware that they have the disease

There are three major types of diabetes:

Type 1 diabetes - Results from the body's failure to produce insulin, the hormone that "unlocks" the cells of the body, allowing glucose to enter and fuel them. It is estimated that 5-10% of Americans who are diagnosed with diabetes have type 1 diabetes.

Type 2 diabetes - Results from insulin resistance (a condition in which the body fails to properly use insulin), combined with relative insulin deficiency. Approximately 90-95% (16 million) have type 2 diabetes.

Pre-diabetes - Pre-diabetes is a condition that occurs when a person's blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 diabetes. It is estimated that at least 16 million Americans have pre-diabetes, in addition to the 17 million with diabetes.

Gestational diabetes - Gestational diabetes affects about 4% of all pregnant women - about 135,000 cases in the United States each year.

http://www.diabetes.org