Internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Doctors of Internal Medicine, also known as internists, are sometimes referred to as the “doctor’s doctor,” because they are often called upon to act as consultants to other physicians to help solve puzzling diagnostic problems. They are especially skilled in the management of patients who have undifferentiated or multi-system disease processes. An internist cares for hospitalized and ambulatory patients and may play a major role in teaching or research.

In modern practice, most internists are subspecialists; that is, in general, they limit their medical practice to problems of one organ system or to one particular area of medical knowledge. For example, gastroenterologists and nephrologists specialize in diseases of the gut and the kidneys, respectively.

Internists have a lengthy clinical and scientific training in their areas of medical interest and have special expertise in the use of prescription drugs or other medical therapies (as opposed to surgery).