Is a DO a medical doctor or a physician's assistant?

D.O. = Doctor of Osteopathic Medicine

The DO is a type of medical physician just like a Doctor of Medicine (M.D.), has the same full medical training, and is certified to handle medical issues and situations. When attending medical school, a DO medical student, in addition to the traditional medical curriculum learned by both DO and MD students (anatomy, biochemistry, histology, pathology, microbiology, etc.) also receive 300-500 hours of instruction in a form of manual therapy known as osteopathic manipulative treatment (OMT).

A Physician's Assistant is known as a "PA".