Internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of diseases.
The medical specialty dedicated to the diagnosis and medical treatment of adults. A physician who specializes in internal medicine is referred to as an internist. Subspecialties of internal medicine include allergy and immunology, cardiology (heart diseases), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumat-ology (arthritis and musculoskeletal disorders).
Doctors who specialize in internal medicine are called internists or general internists. Internal medicine specialists also take a close look at how all the systems in the body work together as a whole because a problem in one area could cause complications in another.
It comes from the German word innere medizin. In the 1800s, German physicians were incorporating knowledge from the sciences of bacteriology (study of bacteria), physiology (study of how the body functions) and pathology (the study of diseases) into their treatment plans. Physicians found the more they understood these subjects, the better equipped they were to help their patients. They were called internal medicine doctors or internists because they focused on the "inner"" diseases instead of the external manifestations of those diseases.