- The initial AOBIM Endocrinology exam is 300 MCQs over seven hours - pacing matters as much as knowledge.
- Passing requires a scaled score of at least 500 on the 200-800 scale, not a raw percentage.
- Diabetes mellitus is the single largest domain at 13-17% - prioritize it early.
- Fellowship must be completed by August 15 of the exam year, with program-director verification required.
What the AOBIM Endocrinology Exam Actually Covers
The American Osteopathic Board of Internal Medicine (AOBIM) administers the initial Endocrinology subspecialty written examination as the credentialing step for osteopathic internists who have completed endocrinology fellowship training. This guide is specifically about that AOBIM initial written exam - not a recertification assessment, and not any other credential that happens to share the "endocrinology" name. If you're still mapping out what the credential entails before you commit to a study plan, our Endocrinology Certification overview and What Is Endocrinology Certification? pages are good starting points.
Because this is a subspecialty exam sitting on top of internal medicine board certification, the question style assumes fluency with core internal medicine but tests depth in hormonal and metabolic disease management, lab interpretation, and clinical decision-making across 18 distinct content areas. Candidates who treat this as "just another internal medicine test" typically underestimate how granular the endocrine-specific questions get.
Eligibility, Fees, and Registration Windows
Before you can sit for the exam, AOBIM requires several eligibility conditions to be met simultaneously:
- Current AOA board certification in internal medicine
- Two years of ACGME-accredited or AOA-recognized endocrinology fellowship training
- An active, unrestricted medical license
- Program-director verification confirming both clinical competence and completion of training
AOBIM specifies that fellowship must be completed by August 15 of the examination year - a hard cutoff that matters if your fellowship end date is close to that line. If you're unsure whether your training pathway qualifies, review the specifics in our Endocrinology Requirements breakdown before you submit anything.
On cost: the standard written examination fee is USD 800. Miss the standard deadline and you'll face a USD 240 late application fee on top of that - a penalty worth avoiding simply by calendaring the window early. For the 2026 cycle, the published application window ran February 16 through July 16, with the initial subspecialty examination itself administered August 12-14. Mark both dates the moment your fellowship program confirms your eligibility timeline. A fuller cost breakdown, including how the late fee interacts with the base fee, lives in our Endocrinology Certification Cost guide, and the full testing calendar is detailed in Endocrinology Exam Dates.
Key Takeaway
Submit your application well before July 16 - the USD 240 late fee is entirely avoidable, and program-director verification can take longer than candidates expect.
Exam Format and Scoring
The initial Endocrinology written exam consists of 300 multiple-choice questions administered over seven hours. That's a long single sitting, and candidates who haven't practiced full-length blocks under timed conditions often find the back half of the exam mentally taxing regardless of how well they know the material.
Scoring works on a 200-800 scaled score, and you need a minimum of 500 to pass. This isn't a straightforward percentage-correct cutoff - it's a scaled result, so don't try to reverse-engineer a "number of questions you can miss." Instead, aim for consistent command across all 18 domains rather than mastering a few and hoping to guess through the rest. For a deeper dive into how the scaled score works and what candidates report about difficulty, see Endocrinology Passing Score and How Hard Is the Endocrinology Exam?. If you want a data-grounded view of outcomes before you plan your timeline, Endocrinology Pass Rate walks through what's actually published.
The 18 Content Domains, Weighted
AOBIM's content outline breaks the exam into 18 official areas, each with a percentage range rather than a fixed weight. That range matters: it tells you where to spend your limited study hours, but it also means the exact proportion of questions can shift slightly from year to year within that band.
Domain 2: Diabetes Mellitus (13-17%)
The single largest domain by a wide margin. Expect deep coverage of insulin regimens, oral and injectable agent selection, complications management, and inpatient/outpatient glycemic control scenarios.
- Know comparative mechanisms and side-effect profiles across drug classes
- Be fluent in complication screening intervals and management
Domains 5 & 6: Hypothyroidism and Hyperthyroidism (6-10% each)
Together these thyroid function domains represent a substantial chunk of the exam. Expect lab-interpretation-heavy questions distinguishing subclinical from overt disease and guiding treatment decisions.
- Master TSH/free T4 patterns across etiologies
- Know when to treat vs. observe in subclinical cases
The remaining domains cover a wide clinical spectrum:
- Domain 1: Principles of endocrinology, hormones, physiology (4-8%)
- Domain 3: Hypoglycemic syndromes/Islet cell disorders (1-5%)
- Domain 4: Lipid disorders (2-6%)
- Domain 7: Tumors of the thyroid (1-5%)
- Domain 8: Disorders of the ovaries/breast (3-7%)
- Domain 9: Menstrual cycle/Fertility/Contraception (1-5%)
- Domain 10: Disorders of the testes (2-6%)
- Domain 11: Disorders of the adrenal cortex (6-10%)
- Domain 12: Disorders of the adrenal medulla/Tumors of adrenal (1-5%)
- Domain 13: Hypothalamic/Pituitary disorders (6-10%)
- Domain 14: Polyglandular/Multiple-Organ syndromes (2-6%)
- Domain 15: Obesity (1-5%)
- Domain 16: Parathyroid disorders/Calcium-phosphorus metabolism (6-10%)
- Domain 17: Bone/Osteoporosis (2-6%)
- Domain 18: Miscellaneous (1-5%)
For a domain-by-domain breakdown with study angles for every single one of these 18 areas, our companion resource Endocrinology Exam Domains 2026: Complete Guide to All 18 Content Areas goes deeper than we have room for here.
| Domain | Weight Range |
|---|---|
| Diabetes Mellitus | 13-17% |
| Hypothyroidism | 6-10% |
| Hyperthyroidism | 6-10% |
| Adrenal Cortex Disorders | 6-10% |
| Hypothalamic/Pituitary Disorders | 6-10% |
| Parathyroid/Calcium-Phosphorus Metabolism | 6-10% |
| Ovarian/Breast Disorders | 3-7% |
| Lipid Disorders | 2-6% |
Building a Domain-Weighted Study Timeline
Generic study techniques - spaced repetition, timed blocks, active recall - all work, but only if you apply them against the actual weight distribution of this exam rather than a generic internal medicine curriculum. Given that diabetes mellitus alone can represent up to 17% of the exam, and four other domains sit in the 6-10% range, a sensible approach front-loads those five heavyweight areas before spending equal time on the narrower 1-5% domains.
Diabetes Mellitus + Hypoglycemic/Islet Cell Disorders
- Drill insulin titration and agent selection scenarios
- Cover complication management and inpatient glycemic protocols
- Layer in islet cell and hypoglycemic syndrome differentials
Thyroid: Hypothyroidism, Hyperthyroidism, Thyroid Tumors
- Build lab-pattern recognition across all thyroid states
- Review nodule workup and thyroid malignancy classification
Adrenal Cortex, Adrenal Medulla, and Pituitary/Hypothalamic Disorders
- Master Cushing's and adrenal insufficiency workups
- Cover pheochromocytoma screening and pituitary axis testing
Parathyroid/Calcium Metabolism, Bone/Osteoporosis, Lipids
- Review calcium-PTH-vitamin D interplay in depth
- Cover osteoporosis treatment thresholds and lipid guideline nuance
Reproductive Endocrinology, Obesity, Polyglandular Syndromes, Miscellaneous
- Cover ovarian, testicular, and fertility-related disorders
- Review MEN syndromes and remaining lower-weight domains
Full-Length Practice and Timing Drills
- Simulate the seven-hour, 300-question format at least twice
- Target weak domains identified from practice performance
If you're building a personalized version of this schedule, our foundational Endocrinology Study Guide 2026: How to Pass on Your First Attempt resource and the quick-reference Endocrinology Cheat Sheet are worth keeping open alongside your primary references. Running full-length timed sets on our practice test platform is one of the most reliable ways to confirm you can sustain accuracy across all seven hours, not just the first ninety minutes.
After You Pass: OCC and Recertification
Passing the initial exam isn't the end of the compliance story. Certification remains active for 10 years, provided you fulfill Osteopathic Continuous Certification (OCC) requirements throughout that period. Maintenance is built around four pillars: active licensure, continuing medical education, a cognitive assessment, and a practice performance assessment.
For time-limited certificate holders, the CME requirement is 60 credits per three-year cycle, which must include at least 15 Category 1 and/or Category 1-A credits for the 2025-2027 cycle. Endocrinology sits within AOBIM's traditional subspecialty OCC examination pathway, meaning the recertification assessment is a separate test from the initial exam - administered annually in August via remote proctoring, rather than the single in-person-style initial exam window described above. Don't conflate the two: the initial exam's 300-question, seven-hour format and 500-point passing threshold apply only to first-time certification, not to the OCC recertification exam that follows years later.
Understanding this long arc matters when you're deciding whether to pursue the credential in the first place. If you're weighing the investment against the career payoff, our analysis in Is the Endocrinology Certification Worth It? Complete ROI Analysis 2026 and the practical outlook in Endocrinology Jobs and Endocrinology Salary Guide 2026 can help frame the decision alongside the pure exam-prep questions this guide answers. And if terminology is still tripping you up - what the credential formally means, what it stands for, or how it differs from related titles - our glossary-style pieces like What Is Endocrinology?, Endocrinology Meaning, and What Does Endocrinology Stand For? fill in that background.
Key Takeaway
Budget for OCC from day one of holding certification - 60 CME credits every three years (15 of which must be Category 1/1-A for 2025-2027) is an ongoing commitment, not a one-time task.
Frequently Asked Questions
The initial exam contains 300 multiple-choice questions administered over seven hours in a single sitting.
You need a scaled score of at least 500 on AOBIM's 200-800 scale - not a fixed percentage of questions correct.
You can still apply late, but you'll pay a USD 240 late application fee in addition to the standard USD 800 written exam fee.
Yes. AOBIM requires two years of ACGME-accredited or AOA-recognized endocrinology fellowship training, with completion verified by your program director and finished by August 15 of the exam year.
No. The OCC recertification exam is a separate, remote-proctored assessment offered annually in August, distinct from the 300-question, seven-hour initial written exam.
Whichever stage of preparation you're at, working through full-length, domain-weighted practice sets on our practice exam platform alongside the resources linked throughout this guide is the most direct path to walking into your August test date fully prepared.