Internal Medicine specialists deliver advanced options for primary care. Internists specialize in diagnosing and treating diseases of the body's internal organs, but they also provide primary care for many of their patients. In addition, they refer patients to specialists, especially if they may need surgery. Internists specialize in adult health care, with at least three years of specialized medical training in adult internal organ function(s). Although they do not perform surgery, Internal Medicine Doctors can diagnose and effectively treat a variety of chronic and acute conditions in patients ranging from teen-to-geriatric age.