Diabetes: An inability of insulin, a hormone produced by the pancreas, to regulate the amount of glucose (sugars) in the blood.

Type 1 diabetes typically occurs in childhood and is characterized by an inability of the pancreas to produce insulin; this type of diabetes often requires injections of insulin.

Type 2 diabetes, or adult onset diabetes, occurs when the body "resists" insulin and glucose levels remain increased. Therapy with protease inhibitors has been associated with Type 2 diabetes.

Symptoms of diabetes include excessive thirst, frequent urination, unexplained weight loss, increased hunger, vision changes and fatigue. If left unchecked, diabetes can be life threatening.

Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)