The letters after a doctor’s name tell you where they trained, what degree they hold, and what specializations they’ve earned. You might see as few as two letters (MD) or a long string like “MD, PhD, FACS,” and each set carries different information. Here’s what they all mean and why they matter.
Primary Medical Degrees
The first set of initials after a doctor’s name is almost always their medical degree. In the United States, two degrees qualify someone to practice as a physician:
- MD (Doctor of Medicine): The most common physician credential. Earning it requires four years of college, four years of medical school, and three to seven years of residency training. MDs must pass a national licensing exam before they can treat patients independently.
- DO (Doctor of Osteopathic Medicine): DOs attend four-year osteopathic medical schools and complete the same residency training as MDs. Their education includes additional focus on the musculoskeletal system and hands-on body manipulation techniques. Since 2020, MD and DO graduates apply through the same residency matching system, and both have identical legal authority to prescribe medications, perform surgery, and practice in any specialty.
Outside the U.S., you’ll commonly see MBBS or MBBCh, both derived from Latin and meaning “bachelor of medicine, bachelor of surgery.” These are the standard medical degrees in the United Kingdom, India, Australia, and most Commonwealth countries. An MBBS is fully equivalent to an American MD, though the training path differs: students typically enter medical school directly after secondary school and study for five to six years rather than completing a separate bachelor’s degree first. If your doctor trained abroad and lists MBBS after their name, they’ve met the same licensing requirements as any U.S.-trained physician to practice here.
Other Doctoral-Level Clinicians
Not every healthcare provider who goes by “doctor” holds an MD or DO. Several other professions earn doctoral degrees and use the title in clinical settings:
- DDS or DMD (Doctor of Dental Surgery / Doctor of Medical Dentistry): Both are dentistry degrees. The two titles reflect naming preferences at different dental schools, not different levels of training.
- DPM (Doctor of Podiatric Medicine): Podiatrists specialize in conditions of the foot, ankle, and lower leg.
- OD (Doctor of Optometry): Optometrists provide eye exams, diagnose vision problems, and prescribe corrective lenses. They’re distinct from ophthalmologists, who are MDs specializing in eye surgery.
- DNP (Doctor of Nursing Practice): Some nurse practitioners pursue this doctoral degree beyond their master’s-level training, deepening their clinical expertise.
- PsyD (Doctor of Psychology): A clinical doctorate focused on therapy and psychological assessment rather than research.
- DPT (Doctor of Physical Therapy): The current entry-level degree for physical therapists.
Mid-Level Provider Credentials
You’ll sometimes see initials on a clinic door or name badge that don’t include “doctor” at all. These belong to advanced practice providers who diagnose, treat, and prescribe under varying degrees of independence.
NP stands for nurse practitioner. NPs hold at minimum a master’s degree in nursing and complete specialized clinical training. They take health histories, perform physical exams, order and interpret lab work, prescribe medications, and manage both acute and chronic conditions. Some NPs go on to earn a DNP.
PA-C stands for physician assistant, certified. PAs complete graduate-level medical training, typically a master’s program modeled on the medical school curriculum but compressed into about two and a half years. They perform physical exams, diagnose illness, order tests, assist in surgery, and write prescriptions. The “C” confirms they’ve passed their national certification exam.
APRN (Advanced Practice Registered Nurse) is an umbrella credential that covers nurse practitioners, nurse midwives, nurse anesthetists, and clinical nurse specialists. If you see APRN after a name, it tells you the person is an RN with graduate-level clinical training.
Fellowship Designations
Letters like FACS, FACP, or FACC appear after a doctor’s degree and signal membership in a professional college or society. The “F” stands for “Fellow,” and the remaining letters identify the organization.
- FACS: Fellow of the American College of Surgeons
- FACP: Fellow of the American College of Physicians (internal medicine)
- FACC: Fellow of the American College of Cardiology
- FAAP: Fellow of the American Academy of Pediatrics
These aren’t simply handed out. To earn FACS, for example, a surgeon must hold board certification in their surgical specialty, maintain a full and unrestricted medical license, have at least one year of practice after completing all formal training, and demonstrate ongoing commitment to professional education and ethical standards. A credentials committee reviews references and evaluates each applicant individually. Fellowship designations are a reliable sign that a physician has met peer-reviewed standards beyond basic licensure.
Research and Academic Degrees
When you see PhD after a clinician’s name, it means they also hold a research doctorate. Some physicians complete combined MD-PhD programs, spending extra years conducting laboratory or clinical research. A doctor listing both credentials typically works in academic medicine, splitting time between seeing patients and running studies.
Less commonly, you’ll see ScD (Doctor of Science), which is a higher research degree awarded to scientists with an exceptional portfolio of published work, usually well beyond the PhD level. ScD holders in healthcare settings tend to occupy senior academic positions like department chairs or research directors rather than seeing patients day to day.
How to Read a Full Credential String
Doctors list their initials in a specific order: degree first, then licensure or certification, then fellowship designations. So “Jane Smith, MD, FACS” tells you she graduated from medical school (MD) and later earned fellowship in the American College of Surgeons (FACS). “John Lee, DO, PhD, FACC” trained as an osteopathic physician, completed a research doctorate, and earned fellowship in cardiology.
The degree tells you what school they attended. Board certification (often not listed as initials but referenced in their bio) tells you they passed rigorous specialty exams. And fellowship letters tell you a professional society has vetted their ongoing competence. Together, the string gives you a quick snapshot of a provider’s training, specialty, and professional standing.