Diabetes mellitus commonly referred to as Diabetes, is a group of metabolic diseases in which there are high blood sugar levels over a prolonged period. Symptoms of high blood sugar include frequent urination, increased thirst and hunger. This is the common form of diabetes, caused by deficiency of the pancreatic hormone insulin, which fails to metabolize sugars and starch. Sugars accumulate in the blood and urine, and the by-products of alternative fat metabolism disturb the acid–base balance of the blood, causing a risk of convulsions and coma. Diabetes is due to one of two mechanisms: a) Inadequate production of insulin (which is made by the pancreas and lowers blood glucose b) Inadequate sensitivity of cells to the action of insulin. The major complications of diabetes include dangerously elevated blood sugar, abnormally low blood sugar due to diabetes medications, and disease of the blood vessels which can damage the eyes, kidneys, nerves, and heart. Diabetes is diagnosed by blood glucose testing, the glucose tolerance test, and testing of the level of glycosylated hemoglobin.