What Is the Difference Between COMLEX and USMLE?

COMLEX is the licensing exam for DO students. USMLE is the licensing exam for MD students, though many DOs also take it for residency competitiveness. The two exams cover most of the same medical content but differ in four meaningful ways: COMLEX includes osteopathic manipulative medicine (about 10 to 12 percent of the test), COMLEX question stems are shorter and more big-picture while USMLE stems are longer and more granular, USMLE has a tougher curve because every MD student takes it (including students from the most selective schools in the country), and the two exams use entirely different scoring scales. If you're a DO student deciding between taking just COMLEX or adding USMLE, the short answer is that most DOs are best served by mastering COMLEX first and only adding USMLE when a specific residency goal actually requires it.

I've taken both exams. I now tutor DO and MD students through both as my full-time job. This article walks through what those four differences look like in practice, where each exam genuinely matters for residency, and what the day-to-day study implications are if you're trying to decide which path makes sense for you.

What is the COMLEX exam?

COMLEX-USA is the three-level licensing exam series administered by the NBOME for students at osteopathic medical schools. Passing COMLEX is required to graduate from a DO school and to obtain a license to practice as a physician in the United States. The series mirrors USMLE in structure (a preclinical exam, a clinical-knowledge exam, and a third exam typically taken during residency) but it is owned and written by a different testing body and built specifically around the osteopathic curriculum.

Level 1 is taken after preclinical years and has been pass or fail since May 10, 2022. The exam was also restructured on May 7, 2026, dropping from 356 to 320 multiple-choice questions delivered in 8 blocks of 40, with roughly 8 hours of testing time and 60 minutes of scheduled break time. Level 2-CE is taken in third or fourth year and is still scored on the standard COMLEX scale. Level 3 is two full days, around 420 total questions, and includes 26 Clinical Decision-Making cases that are fill-in-the-blank rather than multiple-choice. Most DO students sit for Level 3 during their first year of residency.

Scoring on COMLEX uses a scaled range from 10 to 999. The mean is approximately 500 with a standard deviation of 85. Passing for Level 1 (under the previous scored format) and Level 2-CE is 400. Passing for Level 3 is 350. Only about the 5th to 9th percentile of test takers is needed to pass Level 1 or Level 2-CE, and roughly the 3rd percentile to pass Level 3. The bar is genuinely lower than students assume going in. Most DO students who fail are not failing on content; they're failing on strategy, pacing, or anxiety. (For a deeper look at the failure pattern, see our breakdown of why smart students fail boards.)

The defining feature of COMLEX is osteopathic manipulative medicine. OMM makes up roughly 10 to 12 percent of every COMLEX exam, and OMM concepts can appear inside any clinical vignette as the diagnostic clue or the management answer. A USMLE-only student walking into COMLEX is going to be lost on those questions. There is no equivalent on Step 1 or Step 2.

What is the USMLE exam?

USMLE is the three-step licensing exam series administered by the NBME and FSMB for students at allopathic medical schools. Step 1 is pass or fail (as of January 26, 2022) and is taken after preclinical years. Step 2 Clinical Knowledge is scored on a 1 to 300 scale with a national mean in the mid-240s and a passing score of 218 (the threshold updates periodically and was recently raised from 214). Step 3 is taken during residency.

USMLE does not test OMM. The exam pulls heavily from preclinical basic science (embryology, biochemistry, genetics, microbiology) in a way COMLEX does not, particularly on Step 1. Step 2 CK focuses more on management and diagnosis, much closer in flavor to COMLEX Level 2-CE, but still without OMM and still with longer, more granular question stems.

For DO students, USMLE is optional, not required for licensure. You can graduate, get licensed, and practice medicine in any U.S. state with COMLEX alone. The reason DO students consider USMLE is residency competitiveness, particularly for programs that historically filter on Step scores. The reason DO students should think hard before signing up is that USMLE has a brutal curve, an extra thousand or so dollars in fees, and several months of additional preparation that comes directly out of your COMLEX prep budget.

How are COMLEX and USMLE questions actually different on test day?

The two exams test most of the same diseases. What changes is how the question gets to the answer. USMLE gives you a ton of information and rewards precision. COMLEX gives you the bare minimum and rewards big-picture reasoning. If you only practice on UWorld and walk into COMLEX expecting the same depth of stem, you'll feel like the test is missing half the content. (It isn't. It's a different style.)

Here is what a USMLE stem typically reads like:

A 45-year-old man with a history of hypertension, hyperlipidemia, and type 2 diabetes mellitus presents with substernal chest pressure radiating to the left arm, associated with diaphoresis. Troponin is elevated. ECG shows ST-segment elevation in leads II, III, and aVF. Which of the following is the most appropriate next step?

Here is what a COMLEX stem on the same general topic often looks like:

A 45-year-old man presents with chest discomfort. Vital signs are within normal limits. Which of the following is the most appropriate next step?

That's the whole question. No labs, no ECG, no comorbidities. Five answer choices that all feel partially right or partially wrong. The first time I took COMLEX Level 1, I finished the entire exam three hours early because the questions felt so much shorter than UWorld. I walked out genuinely thinking I had failed. I hadn't. I had just been trained for a different format.

The practical implication: if you study for both exams using only UWorld and only USMLE-style content review, you will underperform on COMLEX even when you know the material cold. You need to practice on a COMLEX-style question bank (TrueLearn COMBANK, COMQUEST) at least some of the time to learn the COMLEX rhythm. The big-picture reasoning is a learned skill, just like the precision-reasoning of USMLE is a learned skill.

How do COMLEX and USMLE differ in content and blueprint weighting?

The biggest content difference is OMM. Nothing else on USMLE substitutes for it. The next-biggest difference is the depth of basic science. USMLE Step 1 has historically tested embryology, niche biochemistry pathways, and inheritance pattern detail that COMLEX rarely asks at the same level of specificity. COMLEX cares more about whether you can identify the diagnosis and pick the answer that best describes the underlying pathophysiology, not which specific enzyme has been deficient since the third week of gestation.

Both exams test the same broad content domains: cardiology, pulmonology, GI, renal, endocrine, neuro, psych, OB/GYN, peds, MSK, ID, derm, heme/onc, and the surgical disciplines. Both test biostatistics, ethics, and patient communication. Both reward strong stem-clue reading: age, acuity, unusual findings, timeline, laterality, labs, and the actual question being asked.

The blueprint weighting differs at the margins. COMLEX gives more weight to musculoskeletal content (about 13 percent), community health and preventive medicine (about 12 percent), and of course OMM. USMLE distributes its weight differently and leans harder on basic science integration on Step 1. None of this changes the high-yield study plan in a meaningful way for first-time test takers. Cover the major systems, do focused question blocks, review thoroughly, and you will be ready for either format. The exceptions are OMM (only on COMLEX) and the deepest basic science material (only really matters for USMLE Step 1, and even there, only if you're aiming for a competitive score).

Why is USMLE often harder than COMLEX for DO students?

The content isn't really harder. The competition is. This is the part that catches DO students by surprise when they think about adding USMLE to their plate.

Every MD student in the country takes USMLE. That includes the students who got into the most selective schools in the country. When you sit for USMLE as a DO student, you're being ranked against a curve that includes students from Harvard, Hopkins, UCSF, and every other top-tier MD program. When you sit for COMLEX, you're being ranked against your fellow DO students. The percentile math comes out very differently.

Practical version: a DO student scoring in the 15th percentile on COMLEX has comfortably passed and will likely match somewhere. The same student sitting for USMLE could end up in the 5th percentile and potentially fail. Same brain, same content knowledge, much tougher curve.

This is why I push back hard when a student already struggling with COMLEX tells me they're "keeping their options open" by also taking USMLE. If you're scoring in the 200s, 300s, or low 400s on COMSAEs, adding USMLE almost always backfires. Students try to study for both, end up using UWorld exclusively because "it's the best question bank," and then they neglect COMLEX-specific prep. They either fail COMLEX, barely pass it, or fail USMLE on top of barely passing COMLEX. Worse outcomes across the board.

Even the students I work with who are crushing COMSAEs in the high 400s and 500s often struggle to hit competitive NBME practice scores. The takeaway: if you're not crushing COMLEX, you're almost certainly going to struggle even more with USMLE. (For score-threshold detail on COMSAEs, see our guide to what counts as a good COMSAE score.)

Should DO students take both COMLEX and USMLE?

Most DOs do not need USMLE. There are four specific situations where it might actually be worth the extra cost and prep time. If none of these describe you, default to COMLEX only.

1. Ultra-competitive specialties. Any ROAD specialty (radiology, ophthalmology, anesthesiology, dermatology) or surgical subspecialty (ortho, neurosurgery, plastics, ENT, urology). These specialties have enough applicants that programs filter on Step scores. USMLE can help, though strong audition performance matters at least as much for DO applicants.
2. Big-name academic programs. UCLA, Mayo Clinic, Johns Hopkins, Stanford, and similar institutions are almost entirely MD and use Step scores as a screening tool. These programs are tough for DO students to match into even with excellent USMLE scores. Reality-check whether the goal is realistic before investing the months.
3. Major metropolitan areas. Big cities concentrate the academic programs in category 2. If you want to match in NYC, LA, Boston, Chicago, or DC at one of the prestigious urban academic centers, USMLE may be a hard prerequisite. Community programs and DO-friendly programs in the surrounding suburbs usually don't require it.
4. Genuinely undecided on specialty and excelling on COMSAEs. If you're scoring 500+ on COMSAEs, your preclinical foundation is solid, and you legitimately have not narrowed your specialty, USMLE keeps doors open. The framing here matters. If you suspect you want a non-competitive specialty in primary care, you probably don't need it. If surgery is genuinely on the table, you probably do.

One important rule on USMLE submissions: it's all or nothing. Once you take a USMLE exam, you must submit every USMLE score you have. You can take Step 2 without taking Step 1, but you cannot fail Step 1 and then submit only a passing Step 2 score. A failed Step 1 follows you forever once it exists. Think carefully before sitting for the exam.

The students who get the most benefit from USMLE are the ones who have already proven they can handle COMLEX. If your COMLEX trajectory looks good and you fall into one of the four categories above, USMLE can meaningfully help your application. If you're struggling with COMLEX, adding USMLE almost always makes the overall outcome worse, not better. Master COMLEX first. Get the passing score in hand. Then layer USMLE if and only if your goals actually call for it.

If you're trying to figure out whether your specific situation calls for USMLE, the free Premeducated Skool community has weekly office hours with physician tutors and a growing library of question breakdowns on both COMLEX and USMLE content. You can DM me directly with your scenario and get a real answer rather than guessing.

How do COMLEX and USMLE scoring scales compare?

COMLEX Level 1 became pass-fail on May 10, 2022, and was further restructured on May 7, 2026 down to 320 questions. Level 2-CE is still scored on the 10 to 999 scale, mean ~500, SD 85, passing 400. Level 3 is scored on the same scale with a passing score of 350. The percentile to pass is quite low: roughly the 5th to 9th percentile on Levels 1 and 2-CE, and roughly the 3rd percentile on Level 3.

USMLE Step 1 is pass-fail (as of January 26, 2022). Step 2 CK is scored on a 1 to 300 scale with the national mean in the mid-240s and a passing score that updates periodically (currently 218, recently raised from 214). Step 3 is scored on the same 1 to 300 scale with a different mean and passing threshold.

The two scales are not directly comparable, which is one reason MD-heavy programs sometimes ask for USMLE even from DO applicants. A residency program comparing a COMLEX Level 2-CE score of 600 against an MD applicant's Step 2 CK of 250 has to do an internal conversion table, and not all programs bother. A USMLE score on the application removes that friction.

Frequently asked questions about COMLEX vs USMLE

Is COMLEX easier than USMLE?

Most DO students find COMLEX content slightly more forgiving than USMLE because the basic science is less granular and the percentile to pass is lower. The curve is also much friendlier because the test taker pool is entirely DO students, not the broader MD population. That said, COMLEX has its own challenge: short, vague question stems that reward big-picture reasoning rather than the precision logic USMLE rewards. Students who train exclusively on UWorld often feel disoriented on COMLEX even when they know the material. Different test, different muscle.

Do DO students have to take USMLE?

No. You can graduate from a DO school, obtain a medical license in any U.S. state, and practice as a physician with COMLEX alone. USMLE is optional for DOs and is taken almost exclusively to strengthen residency applications. If your specialty goals do not involve ultra-competitive fields or MD-exclusive academic programs, you can confidently skip USMLE and focus your prep entirely on COMLEX.

Can MD students take COMLEX?

Generally no. COMLEX is restricted to students enrolled at COCA-accredited osteopathic medical schools, because the exam tests osteopathic manipulative medicine, which is part of the DO curriculum and not the MD curriculum. MD students who want to work in osteopathic-heavy environments sometimes pursue additional OMM training postgraduate, but they do not sit for COMLEX.

What is the OMM section of COMLEX?

OMM (osteopathic manipulative medicine) accounts for roughly 10 to 12 percent of COMLEX content. Questions can appear as dedicated OMM stems (identify the somatic dysfunction, choose the appropriate treatment, recognize a counterstrain point) or embedded inside other clinical vignettes where an OMM finding is the diagnostic clue. Strong COMLEX prep includes dedicated OMM review in the final weeks, often using a combination of Savarese, the OMM section of your school's curriculum, and supplementary YouTube content. There is no equivalent section on any USMLE exam.

Should I take USMLE Step 1 if I am applying to surgery as a DO?

Maybe. The answer depends on the specific surgical subspecialty, your COMLEX trajectory, and your willingness to invest in strong audition performance. DO-friendly surgical programs care about audition performance and letters of recommendation at least as much as Step scores. MD-exclusive academic surgical programs care heavily about Step scores and may not interview DOs regardless. If you're scoring above the 80th percentile on COMSAEs and your goal is competitive matching, USMLE Step 2 CK is often the more useful exam now that Step 1 is pass-fail. Discuss with mentors in your target specialty before committing.

How long does it take to study for both COMLEX and USMLE?

For most DO students who take both, expect 8 to 14 weeks of dedicated study split across the two exams, with the bulk of the time biased toward whichever exam comes first. Many DOs take USMLE first because the basic science is fresher in M2, then sit for COMLEX 2 to 6 weeks later. The risk is burnout and content drift, especially on OMM which has to be reactivated for COMLEX. See our guide on how long to study for COMLEX Level 1 for a detailed breakdown of the dedicated-period timeline.

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