- The AOBIM initial Endocrinology exam is 300 questions over seven hours, scored on a 200-800 scale.
- You need a scaled score of at least 500 to pass - no fixed percentage cutoff exists.
- Diabetes mellitus is the single largest domain at 13-17% of the exam.
- Fellowship must be complete by August 15 of the exam year; the 2026 window ran August 12-14.
Exam Overview at a Glance
This cheat sheet condenses the initial AOBIM Endocrinology subspecialty written examination into one scannable reference. It is built specifically for the American Osteopathic Board of Internal Medicine's initial certifying exam - not a recertification assessment, and not any other credential that happens to share the "Endocrinology" acronym. Keep this page bookmarked alongside our full Endocrinology Study Guide 2026 as your primary review companion during the final stretch before test day.
If you're still confirming that this is the right pathway for your career goals, our companion piece on What Is Endocrinology Certification? walks through the purpose of the credential in more depth. For a broader difficulty assessment beyond just the numbers, see How Hard Is the Endocrinology Exam? Complete Difficulty Guide 2026.
Eligibility Snapshot
Before you can sit for the initial written examination, AOBIM requires all of the following:
- Current AOA board certification in internal medicine
- Two years of ACGME-accredited or AOA-recognized endocrinology fellowship training
- Fellowship training completed by August 15 of the examination year
- An active, unrestricted medical license
- Program-director verification confirming clinical competence and completion of training
These requirements are non-negotiable and are verified before your application is approved, so don't wait until the application window opens to confirm your training dates line up. A full walkthrough of documentation and edge cases lives in Endocrinology Requirements 2026: Eligibility, Prerequisites & How to Qualify.
2026 Dates and Fees
| Item | Detail |
|---|---|
| Application window (2026) | February 16 - July 16 |
| Examination window (2026) | August 12 - 14 |
| Standard written exam fee | USD 800 |
| Late application fee | USD 240 |
| Fellowship completion deadline | August 15 of exam year |
Missing the standard application deadline doesn't disqualify you outright, but it does trigger the USD 240 late fee on top of the base USD 800 exam fee - plan your fellowship paperwork and application submission well before mid-July. A deeper cost breakdown, including how these fees fit into the total cost of pursuing certification, is available in Endocrinology Certification Cost 2026: Complete Pricing Breakdown. For the full logistics picture, including how the OCC recertification calendar differs from the initial exam window, see Endocrinology Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Key Takeaway
Submit your application well inside the February 16-July 16 window. The USD 240 late fee is avoidable with basic calendar discipline.
All 18 Content Domains, Ranked
The AOBIM content outline organizes the exam into 18 official areas, each assigned a percentage range rather than a fixed weight. This matters for planning: a domain listed at 1-5% could appear as rarely as three questions or as often as fifteen questions out of 300, so treat the ranges as guidance on relative priority, not exact question counts.
Domain 2: Diabetes Mellitus (13-17%)
The largest single domain by a wide margin. Expect deep coverage of diagnostic criteria, insulin and non-insulin therapy selection, complications, and inpatient/outpatient management scenarios.
- Highest-yield domain on the entire exam - allocate proportionally more review time here
| Domain | Weight |
|---|---|
| 1. Principles of endocrinology, hormones, physiology | 4-8% |
| 2. Diabetes mellitus | 13-17% |
| 3. Hypoglycemic syndromes/Islet cell disorders | 1-5% |
| 4. Lipid disorders | 2-6% |
| 5. Hypothyroidism | 6-10% |
| 6. Hyperthyroidism | 6-10% |
| 7. Tumors of the thyroid | 1-5% |
| 8. Disorders of the ovaries/breast | 3-7% |
| 9. Menstrual cycle/Fertility/Contraception | 1-5% |
| 10. Disorders of the testes | 2-6% |
| 11. Disorders of the adrenal cortex | 6-10% |
| 12. Disorders of the adrenal medulla/Tumors of adrenal | 1-5% |
| 13. Hypothalamic/Pituitary disorders | 6-10% |
| 14. Polyglandular/Multiple-Organ syndromes | 2-6% |
| 15. Obesity | 1-5% |
| 16. Parathyroid disorders/Calcium-phosphorus metabolism | 6-10% |
| 17. Bone/Osteoporosis | 2-6% |
| 18. Miscellaneous | 1-5% |
Six domains sit in the 6-10% band (Hypothyroidism, Hyperthyroidism, Adrenal cortex, Hypothalamic/Pituitary, and Parathyroid/Calcium metabolism) - together they represent the "second tier" of priority after diabetes. For a domain-by-domain breakdown with clinical detail and sample question logic, see Endocrinology Exam Domains 2026: Complete Guide to All 18 Content Areas.
High-Yield Facts by System
Below is a rapid-fire review organized by the body systems most heavily represented on the exam. This is not exhaustive - pair it with case-based question practice to reinforce recall under exam-style conditions.
Thyroid (Domains 5-7, roughly 13-25% combined)
- Distinguish primary vs. central hypothyroidism using TSH/free T4 patterns
- Know first-line and second-line therapy for Graves' disease, toxic nodules, and thyroiditis subtypes
- Thyroid nodule workup: ultrasound risk stratification, fine-needle aspiration cytology categories, and when surveillance vs. biopsy is indicated
Adrenal (Domains 11-12, roughly 7-15% combined)
- Primary vs. secondary adrenal insufficiency - cosyntropin stimulation testing interpretation
- Cushing syndrome: screening tests, localization, and distinguishing ACTH-dependent from ACTH-independent causes
- Pheochromocytoma: biochemical confirmation before imaging, and perioperative management principles
Pituitary and Hypothalamus (Domain 13, 6-10%)
- Prolactinoma management thresholds and medical vs. surgical decision points
- Anterior vs. posterior pituitary hormone deficiency patterns
- Diabetes insipidus vs. SIADH differentiation using serum and urine osmolality
Bone and Mineral Metabolism (Domains 16-17, roughly 8-16% combined)
- Primary hyperparathyroidism diagnostic criteria and surgical indications
- Osteoporosis: DEXA T-score interpretation, FRAX-informed treatment thresholds, and pharmacologic sequencing
- Vitamin D and calcium disorders in the context of renal and GI comorbidities
Scoring and Pass Threshold
The initial examination uses a scaled score from 200 to 800, and candidates must reach at least 500 to pass. This scaled approach means raw question counts don't translate directly to a percentage - there is no publicly stated "you must get X of 300 correct" formula, so resist the urge to reverse-engineer a raw cutoff from the scale numbers. For a focused explanation of what the scaled score actually means for your prep strategy, read Endocrinology Passing Score 2026: Exactly What You Need to Pass. If you want additional context on how outcomes have trended, Endocrinology Pass Rate 2026: What the Data Shows covers what's publicly available.
Key Takeaway
Focus your energy on mastering the highest-weighted domains rather than trying to calculate a precise raw-score target - the scaled scoring model makes that math unreliable.
After You Pass: OCC Requirements
Passing the initial exam is not the end of the certification lifecycle. Certification remains active for 10 years provided Osteopathic Continuous Certification (OCC) requirements are met throughout that period. OCC has multiple components:
- Active licensure maintained continuously
- CME credits - time-limited certificate holders need 60 CME credits per three-year cycle, including 15 Category 1 and/or Category 1-A credits for the 2025-2027 cycle
- Cognitive assessment component
- Practice performance assessment component
Endocrinology sits within AOBIM's traditional subspecialty OCC examination pathway, and those recertification exams are offered annually in August via remote proctoring. It's important to keep this separate in your mind from the initial 300-question, seven-hour written exam described above - the formats and logistics differ, even though both fall under the AOBIM umbrella. If you're still years away from recertification, focus your current energy on the initial exam and revisit OCC planning closer to your certification's expiration.
Final-Week Review Plan
A short, targeted timeline in the days before your exam window (August 12-14) helps consolidate what you've already learned rather than cramming new material.
Diabetes and Thyroid Consolidation
- Redo missed practice questions from Domains 2, 5, and 6
- Review insulin regimen decision trees and thyroid function test patterns
Adrenal, Pituitary, and Bone/Mineral
- Drill adrenal insufficiency and Cushing syndrome workups (Domains 11-12)
- Review pituitary axis testing and parathyroid/calcium disorders (Domains 13, 16-17)
Lower-Weight Domains Sweep
- Quick pass through lipid disorders, obesity, reproductive endocrinology, and polyglandular syndromes
- Don't chase depth here - focus on recognizing classic presentations
Logistics and Light Review
- Confirm remote proctoring or test-center requirements
- Light review of this cheat sheet only - avoid new material
For a full-length study plan spanning months rather than days, our Endocrinology Study Guide 2026 lays out week-by-week pacing across all 18 domains. And if you're weighing whether the time and cost investment makes sense relative to your career plans, Is the Endocrinology Certification Worth It? Complete ROI Analysis 2026 and Endocrinology Salary Guide 2026: Complete Earnings Analysis are useful companion reads. You can also start running timed practice sets right now on our practice test platform to see where your domain-level weaknesses actually are before committing to a fixed schedule.
FAQ
The initial written examination contains 300 multiple-choice questions administered over seven hours.
You need a scaled score of at least 500 on the 200-800 scale used for the initial examination.
Diabetes mellitus (Domain 2) carries the highest weight at 13-17%, making it the single most important domain to master.
AOBIM requires fellowship completion by August 15 of the examination year, alongside AOA board certification in internal medicine and program-director verification.
A late application fee of USD 240 applies on top of the standard USD 800 written exam fee, so submitting within the published window avoids the extra cost.
Keep this cheat sheet handy as a quick-reference companion, but pair it with full domain review and timed practice sets to build the recall speed the seven-hour format demands.