Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced. This high blood sugar produces the classical symptoms of polyuria (frequent urination), polydipsia (increased thirst) and polyphagia (increased hunger).

The three main types of diabetes mellitus (DM) are:

Other forms of diabetes mellitus include congenital diabetes, which is due to genetic defects of insulin secretion, cystic fibrosis-related diabetes, steroid diabetes induced by high doses of glucocorticoids, and several forms of monogenic diabetes.

All forms of diabetes have been treatable since insulin became available in 1921, and type 2 diabetes may be controlled with medications. Both types 1 and 2 are chronic conditions that usually cannot be cured. Pancreas transplants have been tried with limited success in type 1 DM; gastric bypass surgery has been successful in many with morbid obesity and type 2 DM. Gestational diabetes usually resolves after delivery. Diabetes without proper treatments can cause many complications. Acute complications include hypoglycemia, diabetic ketoacidosis, or nonketotic hyperosmolar coma. Serious long-term complications include cardiovascular disease, chronic renal failure, and diabetic retinopathy (retinal damage). Adequate treatment of diabetes is thus important, as well as blood pressure control and lifestyle factors such as smoking cessation and maintaining a healthy body weight.

Drauzio Varella, MD, (b. January 1, 1943 in São Paulo, Brazil) is a Brazilian physician, educator, scientist and noted medical science popularizer in the press and TV, as well as best-selling author. In addition to medicine, Varella is noted as a public commentator on issues such as prison conditions, social welfare, government, literature and his professed atheism and skepticism.

Varella came from a family of Portuguese and Spanish descent from São Paulo. He studied medicine at the Medical School of the University of São Paulo. While a student, he was one of the founders of a pre-med preparatory course with João Carlos di Genio and other colleagues, and where he taught chemistry for several years. This course later became the larger private educational system in Brazil, the Universidade Paulista and the Sistema Objetivo. Varella has won the prestigious Prêmio Jabuti literary award.

After graduation, he specialized in infectious diseases with Prof. Vicente Amato Neto, at the University of São Paulo and at the Hospital do Servidor Público de São Paulo. This work led him to develop an interest in immunology and in the last 20 years he worked at the Hospital do Câncer of São Paulo, specializing in oncology.