The NBME exam refers to any assessment created by the National Board of Medical Examiners, the organization responsible for designing and administering standardized tests throughout medical education in the United States. Most people asking about “the NBME exam” are encountering one of two things: the USMLE licensing exams or the Subject Exams (commonly called “Shelf exams”) taken during medical school clerkships. The NBME also produces self-assessments, international exams, and comprehensive exams used to gauge readiness at key milestones.
Types of NBME Exams
The NBME isn’t a single test. It’s a family of assessments that spans the entire medical training timeline. The major categories include:
- United States Medical Licensing Examination (USMLE): The three-step licensing exam sequence required to practice medicine in the U.S., co-sponsored by the NBME and the Federation of State Medical Boards.
- Subject Exams (Shelf Exams): End-of-rotation tests covering specific clinical and basic science disciplines.
- Comprehensive Exams: Broad assessments used to evaluate readiness for USMLE Step 1 and Step 2.
- Self-Assessments: Practice tools that estimate your probability of passing the USMLE.
- International Foundations of Medicine (IFOM): Exams for medical students and graduates outside the United States.
The USMLE: Steps 1, 2, and 3
The USMLE is the highest-stakes exam the NBME produces. It consists of three steps that medical students and graduates must pass to obtain a license to practice medicine in any U.S. state. The NBME develops the exam content, while the Federation of State Medical Boards co-sponsors the program and manages its role in state licensing.
Step 1 covers foundational science knowledge and is typically taken after the second year of medical school. Since January 26, 2022, Step 1 results are reported as pass/fail only, ending the era of three-digit scores that residency programs once used to rank applicants. Step 2 CK (Clinical Knowledge) tests clinical reasoning and is taken during the third or fourth year. It still carries a numeric score, with a current minimum passing score of 218. Step 3 is taken during or after residency training and focuses on independent patient management.
Subject Exams (Shelf Exams)
When medical students refer casually to “NBME exams,” they often mean the Subject Exams, nicknamed “Shelf exams” because they were historically kept on a shelf and handed out at test time. These are standardized, multiple-choice tests given at the end of a clerkship rotation to measure what you’ve learned in that discipline.
Clinical Science Subject Exams are the most common variety, typically taken during the third year. They cover medicine, surgery, pediatrics, obstetrics and gynecology, psychiatry, clinical neurology, ambulatory care, and family medicine. Most clinical shelf exams contain 110 questions and last 2 hours and 45 minutes. Family medicine is modular, with a core section of 90 questions and optional add-on modules that extend the exam to 100 or 110 questions.
Basic Science Subject Exams exist for preclinical courses like pathology, pharmacology, physiology, biochemistry, microbiology, neurosciences, and anatomy. These typically have 125 questions and run about 3 hours and 8 minutes, though combined exams (like microbiology plus immunology at 150 questions) run longer.
Advanced Clinical Science Subject Exams target fourth-year students. Emergency medicine and internal medicine are the available options, with 110 and 100 questions respectively. Medical schools decide which shelf exams to require and how much weight they carry in your final clerkship grade.
Comprehensive and Readiness Exams
The NBME also offers comprehensive exams designed to measure overall readiness rather than knowledge in a single discipline. The Comprehensive Basic Science Exam contains 200 questions over about 5 hours and 15 minutes (including an optional break), and the Comprehensive Clinical Science Exam has the same structure. Schools use these to assess whether students are prepared to sit for USMLE Step 1 or Step 2.
Self-assessments serve a similar purpose but are designed for individual use. The Comprehensive Basic Science Self-Assessment, for example, provides an estimated probability of passing Step 1. It comes in two formats: a standard-paced version with four sections of 50 questions (1 hour and 15 minutes per section) that mimics the real testing environment, and a self-paced version that extends each section to 5 hours so you can study as you go. These are popular tools for gauging where you stand before committing to an exam date.
International Foundations of Medicine
The IFOM exams are built for medical students and graduates outside the United States. The IFOM Basic Science Exam and IFOM Clinical Science Exam each contain 160 questions and take about 4 hours and 15 minutes. Schools, training programs, and individual test-takers use them for benchmarking knowledge against a U.S.-calibrated standard. They also help international medical graduates strengthen applications for residency programs in the United States. Any current medical student or medical school graduate is eligible to register.
How the Exams Are Administered
NBME exams are delivered either through a school’s own testing setup or at Prometric test centers, a worldwide network of about 350 secure testing facilities. USMLE Step exams are taken at Prometric. Many Subject Exams and comprehensive exams can also be ordered for Prometric administration when a school prefers a proctored, off-campus environment.
For Prometric-based exams, your school submits a roster, and the NBME generates individual scheduling permits within 2 to 3 business days. You then receive an email with instructions to print your permit and book your appointment through Prometric’s website. Rescheduling or canceling within 15 days of your appointment triggers a fee from Prometric. Students who need testing accommodations schedule by phone rather than online. Personal items are not allowed in the secure testing room.
For school-administered web exams, the process is simpler. Your school handles the logistics, and you take the test on-site during a scheduled window. Every web-based exam begins with a 15-minute tutorial before the clock starts on your actual questions.
How Shelf Exams Are Scored
Subject Exam scores are reported on a standardized scale rather than a simple percentage. Your school receives both your individual score and national comparison data, and most programs convert that into a grade for your clerkship. Because the NBME equates scores across different exam forms, a score on one version of the surgery shelf is comparable to a score on another, even though the specific questions differ. How much the shelf exam counts toward your final rotation grade varies by school, but it commonly represents a significant portion.