A physician is someone who holds either a Doctor of Medicine (MD) or Doctor of Osteopathic Medicine (DO) degree, has passed national licensing exams, and holds an active state license to practice medicine. In the United States, the title “physician” is legally protected. New York state law, for example, explicitly states that only a person licensed under its medical practice act may use the title “physician.” Most states have similar protections.
Two Types of Medical Degrees Qualify
The U.S. recognizes two degree pathways that lead to practicing as a physician. An MD (Doctor of Medicine) comes from an allopathic medical school, while a DO (Doctor of Osteopathic Medicine) comes from an osteopathic medical school. Both degrees carry the same legal weight for licensure and practice authority. State licensing boards across the country accept both.
The main difference is philosophical. Osteopathic programs describe their approach as more holistic, emphasizing a mind-body connection and including training in osteopathic manipulative treatment, a hands-on diagnostic and treatment technique. In practice, MDs and DOs work in the same hospitals, the same specialties, and treat the same patients. A board-certified DO surgeon and a board-certified MD surgeon have identical practice authority.
The Training Timeline
Becoming a physician takes a minimum of 11 years of education and training after high school. That breaks down into three stages: four years of undergraduate study (including premedical coursework in biology, chemistry, physics, and math), four years of medical school earning either an MD or DO, and then residency training that ranges from three to seven years depending on the specialty.
Family medicine and pediatrics residencies run three years. General surgery requires five. Subspecialties like cardiothoracic surgery or neurosurgery can push the total even longer when fellowship training is added on top of residency. During residency, physicians hold a restricted license and treat patients under supervision while building independent competence.
Licensing: What Makes It Official
A medical degree alone doesn’t make someone a physician in any legal sense. Licensure does. To receive a state medical license, a graduate must pass a series of national exams. MD graduates take the United States Medical Licensing Examination (USMLE), while DO graduates take the Comprehensive Osteopathic Medical Licensing Examination (COMLEX-USA). The Federation of State Medical Boards recognizes both exams as valid for licensure, and all state medical boards accept them.
Each state issues its own license, so a physician licensed in California isn’t automatically licensed in Texas. Moving states or practicing across state lines requires a separate application. The license is the legal instrument that grants the right to diagnose disease, prescribe medication, perform procedures, and use the title “physician.”
Board Certification vs. Licensure
There’s an important distinction between being licensed and being board certified. A state license is mandatory to practice medicine at all. Board certification, administered through the American Board of Medical Specialties, is voluntary. It signals that a physician has completed additional testing and evaluation in a specific specialty like internal medicine, orthopedic surgery, or psychiatry.
Most hospitals and insurance networks require board certification for credentialing, so in practical terms it’s close to mandatory for physicians who want full career opportunities. But legally, a licensed physician without board certification can still practice medicine within the scope allowed by their state.
Where the Line Gets Complicated
The definition of “physician” isn’t always black and white, especially under federal programs. Podiatrists, who hold a Doctor of Podiatric Medicine (DPM) degree, are included within the definition of “physician” under Medicare, but only for the specific functions their state license authorizes them to perform. A podiatrist can certify medical necessity for certain services and establish home health plans of treatment, functions that normally require a physician. This limited inclusion applies to federal reimbursement purposes and doesn’t mean podiatrists hold the same general practice authority as MDs or DOs.
Nurse practitioners and physician assistants are licensed clinicians who can diagnose conditions and prescribe medications, and nurse practitioners practice independently in more than 30 states. However, neither group holds the title of physician. Their training follows a different path, typically a master’s or doctoral nursing or physician assistant program rather than medical school and residency. The scope of what they can do varies significantly by state law.
International Medical Graduates
Doctors trained outside the United States can become licensed physicians here, but the process involves additional verification. An international medical graduate (IMG) must first earn certification from ECFMG (the Educational Commission for Foreign Medical Graduates). This requires graduating from a medical school listed in the World Directory of Medical Schools, passing Step 1 and Step 2 of the USMLE, and meeting clinical and communication skills requirements, including an English proficiency test.
After ECFMG certification, the IMG must complete a U.S. residency program and then apply for state licensure, just like a domestically trained graduate. The medical degree they earned abroad (often called an MBBS in many countries) is considered equivalent for these purposes, but only after this full credentialing process is complete. Simply holding a foreign medical degree does not grant physician status in the U.S.
How Many Physicians Practice in the U.S.
As of 2023, the United States had 1,010,892 active physicians, according to data from the Association of American Medical Colleges. Of those, 851,282 were in direct patient care, working out to roughly 254 patient care physicians per 100,000 people. The remainder work in research, administration, teaching, or other non-clinical roles while still holding active medical licenses.