A fellow in medicine is a doctor who has already completed medical school and residency and is now pursuing additional training in a narrow subspecialty. Fellowship is the final stage of formal medical education, sitting between residency and fully independent practice as an attending physician. It typically lasts one to three years, depending on the subspecialty.
Where Fellowship Fits in Medical Training
The path to becoming a fully independent physician in the United States follows a set sequence: four years of medical school, three to seven years of residency (depending on the specialty), and then, optionally, fellowship. Not every doctor completes a fellowship. A physician who finishes an internal medicine residency, for example, can practice as a general internist without any further training. But a doctor who wants to specialize in cardiology, gastroenterology, or infectious diseases needs to complete a fellowship first.
Think of residency as learning a broad field and fellowship as narrowing the focus. A surgery resident learns general surgical skills. A surgical fellow might spend additional years focusing exclusively on transplant surgery or surgical oncology. The same principle applies across every area of medicine.
What Fellows Actually Do
Fellows occupy an unusual position: they are licensed, board-certified physicians in their general specialty, but they are still trainees in their subspecialty. This means they carry more responsibility and clinical autonomy than residents, but they still work under the supervision of attending physicians who have completed the same subspecialty training.
The day-to-day balance between clinical work, research, and teaching varies significantly from one fellowship to the next. Some programs are heavily clinical, with fellows spending the majority of their time seeing patients and performing procedures. Others dedicate substantial time to research, particularly in academic medical centers where publishing is expected. Many fellows also teach residents and medical students, serving as a bridge between trainees and attendings. Some programs split time roughly 50/50 between clinical duties and other responsibilities like research and education, while others are almost entirely patient-facing.
How Long Fellowship Takes
Most fellowships last one to three years beyond residency. The exact length depends on the subspecialty and how advanced the training is. A geriatric medicine fellowship after internal medicine residency, for instance, is typically one year. Cardiology requires three years. Some ultra-specialized tracks, like interventional cardiology or transplant surgery, add another year or two on top of an already completed fellowship, meaning a doctor might spend over a decade in training after college.
Here’s how the math works for a common path: four years of college, four years of medical school, three years of internal medicine residency, and three years of cardiology fellowship. That’s 14 years of education and training before practicing independently as a cardiologist.
Common Subspecialties That Require Fellowship
The range of available fellowships is enormous. Internal medicine alone branches into dozens of subspecialties. Mayo Clinic’s graduate medical education program, for example, lists fellowships in areas including:
- Cardiovascular diseases, with further sub-fellowships in electrophysiology, interventional cardiology, heart failure, and echocardiography
- Gastroenterology and hepatology, including advanced endoscopy, inflammatory bowel disease, and transplant hepatology
- Pulmonary and critical care medicine, with tracks in interstitial lung disease, pulmonary hypertension, and interventional pulmonology
- Hematology and oncology, including blood and marrow transplant
- Nephrology, with subspecialty options in transplant, glomerular diseases, and onco-nephrology
- Infectious diseases, including transplant-related infections and orthopedic infections
- Rheumatology, endocrinology, allergy and immunology, sleep medicine, hospice and palliative medicine, and geriatric medicine
Fellowship options exist outside of internal medicine too. Surgical specialties, pediatrics, emergency medicine, radiology, and pathology all have subspecialty fellowship tracks.
How Fellows Are Selected
Most fellowship positions are filled through a formal matching process run by the National Resident Matching Program (NRMP), the same organization that matches medical students into residencies. The process has three main phases: registration, ranking, and results. Residents typically apply during their final years of residency, interview at programs across the country, and then submit a ranked list of their preferred programs. Programs do the same with their preferred applicants, and a computer algorithm pairs them.
Competition varies widely by subspecialty. Cardiology and gastroenterology fellowships are notoriously competitive, while some other subspecialties have more available positions relative to applicants. International medical graduates (doctors who attended medical school outside the U.S. or Canada) must hold certification from the Educational Commission for Foreign Medical Graduates before entering an accredited fellowship.
Fellow Pay and Benefits
Fellows are paid on the same scale as residents, with salary increasing by training year rather than by title. At the University of Michigan, for example, annual salaries for the 2026-2027 academic year range from about $77,000 for a first-year trainee to roughly $105,000 for a ninth-year trainee. A fellow who is in their seventh overall year of post-medical-school training (three years of residency plus four years of fellowship) would earn around $97,000.
These salaries are a fraction of what attending physicians earn, which is one reason fellowship represents a real financial trade-off. A doctor choosing a three-year fellowship is delaying three years of attending-level income, which in many specialties exceeds $300,000 annually. Benefits, however, are generally solid: health insurance starting on day one, life insurance, professional liability coverage, long-term disability, and various leave policies including paid parental leave.
Board Certification After Fellowship
Completing a fellowship makes a physician eligible to sit for subspecialty board certification through one of the member boards of the American Board of Medical Specialties (ABMS). The requirements for certification include finishing an ACGME-accredited training program, holding an unrestricted medical license, and receiving an attestation from the fellowship program director confirming the fellow is ready for independent practice.
Most subspecialties also require that the fellow already hold general board certification in the underlying specialty. A cardiology fellow, for instance, needs to be certified in internal medicine before pursuing subspecialty certification in cardiovascular disease. Some subspecialties have additional requirements beyond training completion, such as documented case lists or practice-based performance improvement activities.
Fellow vs. Resident vs. Attending
If you encounter these titles in a hospital, here’s the practical difference. A resident is a doctor still learning their broad specialty. They practice under fairly close supervision and have restrictions on prescribing and clinical decision-making outside their training rotations. A fellow is further along: already fully trained in a general specialty, now learning a subspecialty, and operating with notably more independence. An attending is the supervising physician who has completed all training and holds full, unrestricted clinical privileges.
For patients, the distinction matters less than it might seem. Fellows are experienced doctors who have already spent years caring for patients. They simply haven’t yet finished the final phase of their subspecialty education. In most clinical settings, a fellow’s work is reviewed by an attending, but the fellow is often the one conducting the detailed evaluation, performing procedures, and explaining the plan to the patient.