A medical doctor (also called a physician) is a person who practices medicine to treat illness and injuries. Medical doctors go to medical school to be trained.They usually hold a college degree in medicine. Medical doctors used to make house calls to treat patients at home. Now they usually see patients in their offices or in hospitals. Medical doctors may also work for schools, companies, sports teams, or the military.edical doctors go to medical school to be trained. They usually hold a college degree in medicine. Medical doctors used to make house calls to treat patients at home. Now they usually see patients in their offices or in hospitals.