A D.O. is a Doctor of Osteopathic Medicine.

D.O.s and M.D.s are alike in that they both use all scientifically accepted methods of diagnosis and treatment, including use of drugs and surgery. Even educational requirements are the same. In most cases, D.O.s and M.D.s are examined by the same state licensing board. One has a M.D. (doctor of medicine) degree, and the other has a D.O. (doctor of osteopathic medicine) degree. They are the only two types of physicians who can practice the full range of medicine.

D.O.s focus on preventive health care.

Osteopathic medical schools emphasize training students to be primary care physicians.

D.O.s practice a "whole person" approach to medicine. Instead of just treating specific symptoms or illnesses, they regard the body as an integrated whole.

The D.O.s’ medical philosophy embraces the concept that the musculoskeletal system (the muscles, bones, and joints) is interdependent, and a disturbance in one area causes altered functions in other body systems. D.O.s use structural diagnosis and OMT, or osteopathic manipulative therapy, along with all traditional forms of diagnosis and treatment such as drugs and surgery to care for patients.