Doctors of Internal Medicine focus on adult medicine and have had special study and training focusing in the prevention and treatment of adult diseases. At least three of their seven or more years of medical school and postgraduate training are dedicated to learning how to prevent, diagnose, and treat diseases that affect adults. Internists are sometimes referred to as the doctor, because they are often called upon to act as the consultants to other physicians to help solve puzzling diagnostic problems.

Internists are equipped to deal with whatever problem a patient brings no matter how common or rare, or how simple or complex. They are specially trained to solve puzzling diagnostic problems and can handle severe chronic illnesses and situations where several different illnesses may strike at the same time. They also bring to patients an understanding of wellness, disease prevention and the promotion of health.