Subspecialties of internal medicine

Internists can choose to focus their practice on general internal medicine, or may take additional training to "subspecialize" in one of 13 areas of internal medicine, generally organized by organ system. Cardiologists, for example, are doctors of internal medicine who subspecialize in diseases of the heart. The training an internist receives to subspecialize in a particular medical area is both broad and deep. Subspecialty training (often called a "fellowship") usually requires an additional one to three years beyond the standard three year general internal medicine residency. (Residencies come after a student has graduated from medical school.)

In the United States, there are two organizations responsible for certification of subspecialists within the field, the American Board of Internal Medicine, and the American Osteopathic Board of Internal Medicine.

The following are the subspecialties recognized by the American Board of Internal Medicine.

* Cardiology, dealing with disorders of the heart and blood vessels
* Endocrinology, dealing with disorders of the endocrine system and its specific secretions called hormones
* Gastroenterology, concerned with the field of digestive diseases
* Hematology, concerned with blood, the blood-forming organs and its disorders
* Infectious disease, concerned with disease caused by a biological agent such as by a virus, bacterium or parasite
* Medical oncology, dealing with the study and treatment of cancer
* Nephrology, dealing with the study of the function and diseases of the kidney
* Pulmonology, dealing with diseases of the lungs and the respiratory tract
* Rheumatology, devoted to the diagnosis and therapy of rheumatic diseases.