Internal medicine deals with the diagnosis and treatment of many diseases. This branch covers a wide range of conditions affecting the internal organs of the body. For example, the lungs, heart, gastrointestinal system, liver, urinary tract and kidneys, spine, nerves, muscles and joints are the subject of internal medicine.

Sub-branches of internal medicine include rheumatology (arthritis and musculoskeletal diseases), allergy and immunology, cardiology (heart diseases), endocrinology (hormone diseases), oncology (cancer), pulmonology (lung diseases), infectious diseases, gastroenterology (intestinal diseases), hematology (blood diseases) and nephrology (kidney diseases).