Internal Medicine Information Doctors of internal medicine are specially trained to focus on adult medicine and the prevention, diagnosis and treatment of adult diseases. They provide primary care or complex care to patients ranging in age from teens to the elderly, and see patients in the office, or in a variety of medical settings. Because of their expertise, internal medicine physicians are often called upon to act as consultants to other physicians to help solve puzzling diagnostic problems. Many internists subspecialize in areas such as cardiology, infectious diseases, arthritis and other inflammatory disease, gastroenterology oncology, and other specialty areas.