Diabetes mellitus 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. The fourth edition of Textbook of Diabetes Mellitus has been fully revised to provide clinicians with the latest developments in the field. Divided into 19 sections, the book begins with discussion on the epidemiology, physiology and metabolism of the disease; its diagnosis and classification; and aetiopathogenesis, genetics and hormone action. The following sections cover types of diabetes, including in different segments of the population; clinical features and complications; diabetes with comorbidities; and management of the disease through both pharmacotherapy and non-pharmaceutical methods.