A quick guide to some common credentials among primary-care medical providers:

M.D. — Medical Doctor — Requires a college degree plus four years of medical school and a residency, typically three or four more years, in a medical speciality such as primary care. Has full care rights, including diagnosing illnesses, performing medical procedures and prescribing medications.

D.O. — Doctor of Osteopathy — Same educational, licensing requirements and range of care as medical doctors. They receive extra training on the musculoskeletal system so they can better understand how injury or illness to one part of the body may affect another.

P.A. — Physician Assistant — Requirements vary by state, but typically P.A.s have a college degree plus an advanced degree in a medical specialty. They’re licensed to perform many of the same diagnostic and treatment regimens as M.D.s and D.O.s, but must work under the supervision of a doctor in most states. They take many of the same classes as doctors, allowing them to practice in a variety of specialties.

N.P. — Nurse Practitioner — Requirements vary by state, but typically an N.P. has a college degree in nursing plus an advanced degree in a nursing speciality, such as primary care. Some nurse practitioners work in clinics without direct doctor supervision. Others work together with doctors as a joint health care team. Their scope of practice and authority depends on state laws.

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