Diabetes mellitus is a common metabolic endocrinopathy resulting from absolute or relative deficiency of insulin that leads to the metabolic disturbance of carbohydrate, fat and protein.

The typical case of diabetes mellitus is usually featured by polyphagia , polydipsia, polyuria, and decrease of body weight. Early or asymptomatic patients have only the manifestations caused by abnormal release of cortical hormone and insulin in the body i.e. the elevated level of fasting blood sugar and the abnormal glucose tolerance test. The symptomatic patients are usually complicated with other symptoms of dermal, neural and endocrinic disorders in addition to the polyphagia, polydipsia, polyuria and decrease of body weight above mentioned.

The main complications and concomitant diseases of diabetes mellitus are diabetic ketoacidosis, cardiovascular diseases, diabetic renopathy and peripheral neuropathy. Cardiovascualr complications are considered as one of the chief causes of death.

Diabetes mellitus is classified into juvenile and adult types according to the clinical features. The former is characterized by young age of onset and a tendency to inheritance. The blood sugar fluctuates widely and is quite sensitive to insulin. It is difficult to be treated and is easily complicated by ketoacidosis and hypoglycemia, so is often named as insulin-dependent diabetes or unstable diabetes. The adult type is characterized by real adult age and could be controlled by dietary restriction or oral antidiabetics, thus is also called non-insulin-dependent diabetes or stable diabetes.