https://en.wikipedia.org/wiki/Doctor_of_Medicine
In the United States, the M.D. awarded by medical schools is a professional doctorate (as opposed to the Doctor of Philosophy degree which requires a focus on research) and is accredited by the Liaison Committee on Medical Education (LCME), an independent body sponsored by the Association of American Medical Colleges, and the American Medical Association (AMA).
In addition to the M.D., the Doctor of Osteopathic Medicine (D.O.) is an equivalent professional doctoral degree for physicians and surgeons offered by medical schools in the United States. According to Harrison's Principles of Internal Medicine, "the training, practice, credentialing, licensure, and reimbursement of osteopathic physicians is virtually indistinguishable from those of M.D. physicians, with 4 years of osteopathic medical school followed by specialty and subspecialty training and certification."