Diabetes mellitus is impaired insulin secretion and variable degrees of peripheral insulin resistance leading to hyperglycemia. Early symptoms are related to hyperglycemia and include polydipsia, polyphagia, and polyuria. Later complications include vascular disease, peripheral neuropathy, and predisposition to infection. Diagnosis is by measuring plasma glucose. Treatment is diet, exercise, and drugs that reduce glucose levels, including insulin and oral antihyperglycemic drugs. Prognosis varies with degree of glucose control.

There are 2 main categories of diabetes mellitus (DM)—type 1 and type 2, which can be distinguished by a combination of features. Diabetes affects 25.8 million people of all ages, 8.3 percent of the U.S. population - diagnosed 18.8 milion people, undiagnosed 7.0 milion people. Diabetes can be a primary reason for hospitalization or can accompany other illnesses that require inpatient care.