A fellow in medicine is a physician who has already completed medical school and residency training and is now pursuing additional, specialized training in a narrower area of medicine. Think of it as the final stage of formal medical education. A cardiologist, for example, first finishes an internal medicine residency, then enters a cardiology fellowship to gain the focused expertise needed to treat heart conditions. Fellows are fully trained doctors who could practice independently in their broader specialty but choose to spend one to three more years becoming experts in a subspecialty.
Where Fellows Fit in the Training Hierarchy
The path to becoming a fellow is long. It starts with four years of medical school, followed by three to seven years of residency depending on the specialty. Fellowship comes after all of that. By the time physicians reach fellowship, they’ve typically spent a decade or more in medical training.
This prior experience is what separates fellows from residents. Residents are learning to practice medicine broadly within a specialty, handling a wide range of cases under close attending physician supervision. Fellows, by contrast, arrive with that foundation already in place. They focus on advanced, complex cases within a specific niche and operate with considerably more independence. A fellow still works under the guidance of attending physicians, but the supervision is lighter and more consultative. Fellows often lead patient care teams, teach residents, and make clinical decisions with what’s described as “conditional independence.”
What Fellows Actually Do
A fellow’s daily work blends patient care, teaching, and research. On a typical day, a fellow participates in morning rounds, offering input on patient management and helping educate the residents rotating through the service. After rounds, they continue caring for patients under attending supervision, handling the more complex or unusual cases that define their subspecialty.
Teaching is a significant part of the role. Fellows give lectures, present at conferences, and mentor residents who are earlier in their training. Most fellowship programs also expect fellows to participate in at least one research project, ideally leading to a published paper or a presentation at a national meeting. This research component is one reason fellowships exist: they advance the field, not just the individual.
How Long Fellowships Last
Fellowship length varies by subspecialty, typically ranging from one to three years. Some examples from internal medicine subspecialties illustrate the range:
- Cardiovascular diseases: 3 years
- Gastroenterology: 3 years
- Endocrinology, diabetes, and metabolism: 2 to 3 years
- Allergy and immunology: 2 to 3 years
- Interventional cardiology: 2 years (after completing a general cardiology fellowship first)
- Advanced heart failure and transplant cardiology: 1 year (also after general cardiology)
Surgical subspecialties, pediatric subspecialties, and others follow their own timelines. Some physicians pursue more than one fellowship sequentially, adding years to their training. A doctor who subspecializes in interventional cardiology, for instance, completes a three-year internal medicine residency, a three-year cardiovascular diseases fellowship, and then a two-year interventional fellowship.
Common Subspecialties That Require Fellowship
The list of fellowship-trained subspecialties is extensive. Within internal medicine alone, the Accreditation Council for Graduate Medical Education (ACGME) recognizes subspecialties including cardiology, pulmonary and critical care, oncology, hematology, infectious disease, nephrology, rheumatology, gastroenterology, geriatric medicine, sleep medicine, and hospice and palliative medicine.
Pediatrics has its own parallel set: pediatric cardiology, pediatric surgery, pediatric critical care, pediatric endocrinology, pediatric hematology-oncology, and many more. Nearly every major medical field, from surgery to psychiatry to anesthesiology, has subspecialty fellowships branching off from it.
Requirements to Enter Fellowship
To qualify for a fellowship, a physician needs a degree from an accredited medical school (either an MD or DO), completion of a residency in the relevant specialty, passing scores on national licensing exams, and letters of recommendation. International medical graduates must hold a valid certificate from the Educational Commission for Foreign Medical Graduates or an unrestricted U.S. medical license. Any gaps between medical school graduation and the fellowship application need to be documented and explained.
Fellowship positions are competitive. Programs look for strong clinical performance during residency, research experience, and a clear commitment to the subspecialty.
Licensing and Supervision
Fellows hold medical licenses, though the exact type depends on their training stage and state. In some states, physicians in graduate medical education programs train under a postgraduate training license rather than a full, unrestricted physician’s license. In California, for example, international graduates who aren’t yet eligible for a full license can receive a special permit that allows them to practice only within the sponsoring institution and its affiliates.
Regardless of license type, fellows practice under the supervision of attending physicians who are board-certified in the subspecialty. The level of oversight decreases as the fellow gains competence. By the end of training, most fellows function nearly independently, with attending involvement limited to the most complex decisions.
Fellow Pay
Fellows earn a stipend rather than a full physician salary, though the amount increases with each year of postgraduate training. At Mayo Clinic, for reference, stipends for the 2026 academic year range from about $75,000 at the first graduate level to over $106,000 at the tenth. Since most fellows are at least four to seven years into postgraduate training when they start, their stipends typically fall somewhere in the middle of that range. These figures are modest compared to what a fully trained specialist earns, which is one reason fellowship represents a real financial commitment.
What Happens After Fellowship
Completing a fellowship makes a physician eligible to sit for a subspecialty board certification exam administered by the relevant member board of the American Board of Medical Specialties. Passing that exam means the physician is board-certified in their subspecialty, a credential that signals advanced expertise to patients, employers, and peers. After certification, the physician is considered an attending in their subspecialty and can practice independently, join academic medical centers, or enter private practice with full authority in their area of focus.