The COMLEX-USA Exams: A Comprehensive Guide
This exam for osteopathic students is required for medical licensure.
There are three levels of COMLEX at three distinct stages of your medical education and training.
What You'll Learn
Three Levels, Three Career Stages
How COMLEX Level 1, Level 2-CE, and Level 3 map onto medical school, residency prep, and independent licensure.
Level 2-CE Is Now the Key Score
Why Level 2-CE became the top pre-interview screening factor for residency applications after Level 1 moved to Pass/Fail.
COMLEX vs. USMLE
Where the two licensing exam series overlap and where COMLEX's osteopathic focus and format set it apart.
Why Many DO Students Also Take the USMLE
How adding the USMLE can strengthen applications for competitive specialties or urban residency programs.
Upcoming Changes to Level 3
What's changing when Level 3 shifts to a single-day, 8-hour format starting January 2027.
Building an Effective Study Plan
A 6-month prep timeline using question banks and official practice exams to steadily build toward test day.
Why COMLEX Is Tougher Than the MCAT
How COMLEX's advanced clinical reasoning, pacing, and question ambiguity set it apart from the MCAT.
What are the COMLEX exams?
Level 1
Level 2-CE
Level 3
How should DO students prepare for COMLEX?
Frequently asked questions
COMLEX-USA consists of three standardized board exams. Virtually all osteopathic medical students are required to complete Level 1 halfway through medical school, Level 2-CE before medical residency, and Level 3 before medical licensure.
In this guide, we’ll cover what each Level tests, what to study, when you’ll take it, the scoring system, and how COMLEX performance can impact residency applications–including some expert tips and tricks throughout.
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| Level | How it’s scored | Main Purpose |
|---|---|---|
| Level 1 | Pass/Fail | Testing your foundational scientific and osteopathic knowledge before your clinical years of med school (M3, M4) |
| Level 2-CE |
Score range: 9-999 Passing score: 400 (5th percentile) National mean: 530-555 Competitive score: 600 (75th percentile) |
Assessing your clinical knowledge, medical decision-making, and communication skills—among other important traits required to start practicing medicine under supervision |
| Level 3 |
Score range: 9-999 Passing score: 350 (3rd percentile) National mean: 568 |
Evaluating advanced medical knowledge, osteopathic techniques, and decision-making in preparation for independent practice |
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What are the COMLEX exams?
The Comprehensive Osteopathic Medical Licensing Examination of the United States (COMLEX-USA) is a series of three standardized board exams created and administered by the National Board of Osteopathic Medical Examiners (NBOME).
Note: COMLEX is different from the Comprehensive Osteopathic Medical Achievement Test (COMAT). You take COMAT Clinical Subject Exams at the end of each clinical rotation in M3 and M4, and COMAT-SE is a self-assessment to prepare for the COMAT.
Basically, all Doctor of Osteopathic Medicine degree (DO) students are required to take the COMLEX tests. You must take Level 1 and Level 2-CE (Cognitive Evaluation) before applying to medical residency. COMLEX Level 3 is accepted in all 50 states for medical licensure of osteopathic doctors.
There is a similar standardized board exam for Doctor of Medicine (MD) students, called the United States Medical Licensing Examination (USMLE), administered by the National Board of Medical Examiners (NBME). USMLE is also a series of three tests, called Step 1, Step 2-CK (Clinical Knowledge), and Step 3, instead of Level 1, 2-CE, and 3.
Although the USMLE is not required for DO students, more than half take at least one Step—typically to make their residency applications more competitive.
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Level 1
COMLEX-USA Level 1 is the first step towards DO licensure. It’s required at virtually all osteopathic medical schools for graduation, as well as to take Level 2-CE—another requirement for graduation.
Level 1 is a computer-based exam consisting of 352 questions, all multiple choice, over one testing day.
What does it test? (What to study)
Level 1 is meant to test your basic osteopathic competencies before you move into your clinical years of medical school, where you’ll be directly interacting with patients under supervision.
There are two dimensions of Level 1. Here are the subjects and areas you’ll be tested on in Level 1’s first dimension, and where you can focus your studies:
Foundational biomedical sciences (about 75% of the first dimension of Level 1)
Molecular, biochemical, tissue, and cellular bases of health and disease
Medical genetics
Anatomic and structural bases of health and disease
Physiologic and pathologic bases of health and disease
Microbiologic and immunologic bases of health and disease
Pharmacologic principles and pharmacotherapeutics in health and disease
Neurosciences
Biopsychosocial sciences
Epidemiology and population sciences
Osteopathic principles and practice (OPP)
Osteopathic manipulative treatment (OMT)
Osteopathic patient care and procedural skills
Practice-based learning and improvement
Interpersonal and communication skills
Professionalism in an osteopathic context
Systems-based osteopathic medical practice
You’ll be given clinical presentations in the second dimension, in which you’ll be tested on the following content, in order of how much it may appear on the exam:
Musculoskeletal system
Community health and patient presentations related to wellness
Nervous system and mental health
Gastrointestinal system and nutritional health
Circulatory and hematologic systems
Respiratory system
Human development, reproduction, and sexuality
Endocrine system and metabolism
Genitourinary/renal system and breasts
Integumentary system
When do you take it?
DO students generally take Level 1 at the end or right after their second year in medical school (M2), in preparation for their clinical years (M3 and M4).
How is it scored?
In 2022, Level 1 moved from a three-digit grading scale to a binary Pass/Fail grading system. About 90% of osteopathic medical students pass Level 1 each year.
The passing standard is around 400—meaning you need to get about 60% of questions right. However, there is no way for you to know your numerical grade anymore. NBOME only reports whether you passed or failed.
How does Level 1 affect residency applications?
In virtually all cases, you need to pass COMLEX Level 1 in order to be eligible to apply to medical residency programs and further your graduate medical education (GME).
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Level 2-CE
COMLEX-USA Level 2-CE (Clinical Evaluation) is the second test in the COMLEX series, and many consider it to be the most stressful. It’s probably the number one factor in residency application screening, especially after Level 1 moved to a Pass/Fail grading scale.
Level 2 is a computer-based exam consisting of 352 questions, mostly multiple choice, over one testing day.
In 2020, COMLEX Level 2-PE (Performance Evaluation) was suspended, and in 2022, it was fully discontinued. This leaves Level 2-CE as the only Level 2 test—meaning we could just call it Level 2—although many still refer to it as Level 2-CE out of precedent.
What does it test? (What to study)
Level 2-CE is designed to assess your ability to practice medicine under supervision. When you graduate, you will be a doctor even if you’re not fully licensed. Level 2 tests whether you’re ready to be responsible for patient care, even under supervision.
Here are the subjects and areas you’ll be tested on in Level 2-CE’s first dimension, and where you can focus your studies, in order of how much they appear on the test:
Osteopathic patient care and procedural skills
Foundational biomedical sciences (about 25% of the first dimension of Level 2)
Application of knowledge for osteopathic medical practice
Osteopathic principles and practice (OPP)
Osteopathic manipulative treatment (OMT)
Practice-based learning and improvement
Professionalism in an osteopathic context
Interpersonal and communication skills
Systems-based osteopathic medical practice
You’ll be given clinical presentations in the second dimension, in which you’ll be tested on the following content, in order of how much it may appear on the exam (similar to Level 1):
Musculoskeletal system
Community health and patient presentations related to wellness
Nervous system and mental health
Gastrointestinal system and nutritional health
Circulatory and hematologic systems
Respiratory system
Human development, reproduction, and sexuality
Endocrine system and metabolism
Genitourinary/renal system and breasts
Integumentary system
When do you take it?
COMLEX Level 2-CE is generally taken after your third year in medical school (M3), in preparation for applying to residencies in the summer between M3 and M4.
Level 2 test dates generally open up at the start of June, and you should be able to schedule your test date up to six months in advance.
Gap years are common before medical school, but not before residency. However, if your personal circumstances require you to delay your residency application by a year, you should be able to take Level 2 after M4. However, Level 2-CE is usually required for colleges of osteopathic medicine to confer a degree, so you will need to officially delay your graduation if this rare circumstance applies to you.
How is it scored?
Level 2-CE is graded on a three-digit scale. You need a 400 to pass, but you want a 500+ to have a chance at residency or a 600+ to be competitive at the top residencies.
Since Level 1 is graded as Pass/Fail, getting a good Level 2 score is now more important than ever for residency applications.
How does Level 2-CE affect residency applications?
Since Level 1 has moved to a Pass/Fail grading system, your COMLEX-USA Level 2-CE score is now the most important pre-interview screening factor for your residency application, next to letters of recommendation, personal statement, and program signals.
If you’re invited to an interview, the interview day becomes the number one factor, of course—they get to know you as an individual and how you’ll fit into their workplace culture. But your Level 2 scores are still paramount to your competitiveness as a residency candidate throughout the process.
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Level 3
COMLEX-USA Level 3 is the final test in the COMLEX series. It’s often the last step before you’re fully licensed to practice medicine independently, without supervision.
Effective January 13, 2027, the NBOME is changing the COMLEX-USA Level 3 examination from a two-day test into a single-day, 8-hour computer-based assessment. The updated format will include 240 multiple-choice questions and 16 clinical decision-making cases split across four testing sessions.
What does it test? (What to study)
COMLEX Level 3 tests your knowledge fluency, clinical skills, medical reasoning, and other core competencies essential for an osteopathic generalist physician.
Here are the subjects and areas you’ll be tested on in Level 3, and where you can focus your studies:
Osteopathic patient care and procedural skills
Application of knowledge for osteopathic medical practice
Osteopathic principles and practice (OPP)
Osteopathic manipulative treatment (OMT)
Foundational biomedical sciences knowledge base (about 10% of Level 3)
Practice-based learning and improvement
Professionalism in an osteopathic context
Systems-based osteopathic medical practice
Interpersonal and communication skills
You’ll be given clinical presentations in the second dimension, in which you’ll be tested on the following content, in order of how much it may appear on the exam (similar to Level 1 and 2):
Musculoskeletal system
Community health and patient presentations related to wellness
Nervous system and mental health
Gastrointestinal system and nutritional health
Circulatory and hematologic systems
Respiratory system
Human development, reproduction, and sexuality
Endocrine system and metabolism
Genitourinary/renal system and breasts
Integumentary system
When do you take it?
Most people take COMLEX Level 3 in PGY-2 (second year of residency), although taking it in PGY-1 is also common, depending on program guidelines and state requirements.
Taking Level 3 later than PGY-2 usually means you failed the first time and need to retake the test. Or maybe you needed to take a leave of absence due to personal circumstances, delaying your licensure.
How is it scored?
Level 3 is graded on a three-digit scale, but most people simply need to pass in order to fulfill state medical board and residency program requirements. The passing score (350) currently sits around the 4th percentile of all test takers.
You may need to aim for a strong score (568+) if you are applying to a fellowship or if there are specific COMLEX requirements for a hospital position you want to fill.
Why does Level 3 matter?
COMLEX Level 3 matters because it is typically the final step to full medical licensure, so that you can satisfy residency graduation requirements and practice medicine independently. Generally, you simply need to pass in order to be eligible for state board licensure.
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How should DO students prepare for COMLEX?
To prepare for the COMLEX-USA and set yourself up for success, you can do the following:
Start preparation early. Make sure you understand what is expected of you and what your test date options are pretty early on. Build your study schedule more than six months out to benefit both your final score and your mental health. Determine whether you’re taking just the COMLEX or if you also plan to take the USMLE.
Build an effective study schedule. Figure out your test date, and then set up a study schedule over the course of six months. This pace should be less stressful than cramming in four weeks, and it gives you plenty of time to figure out and address your weak spots. We recommend studying 10-15 questions a day in your first two months, then moving to 25-30 questions a day in month three. Start taking practice tests every two weeks in month four.
Use practice questions. High-quality question banks can be very useful to prepare for actual exam questions. Unlike full practice tests, you can fit a few practice questions in on break from work, between classes, and at the end of a meal. The best question banks are COMQUEST and AMBOSS.
Take practice exams. The NBOME actually provides a free practice exam, called the COMSAE. The Comprehensive Osteopathic Medical Self-Assessment Examination (COMSAE) series helps you get familiar with the format and feel of the actual quiz. WelCOM is another official practice exam, but it’s lower-stakes—good for early in your study schedule.
Review weak areas. Regular practice questions and practice tests help you know where you need to study more. Identify those weak spots, write them down, and focus on them next time you study. When you plan out your study schedule, work in time to focus on “weak areas,” even though you won’t know what the weak areas are until later.
Incorporate osteopathic principles and practice (OPP) into your prep. You aren’t an MD student. Ensure you’re covering the tenets of osteopathic medicine in your COMLEX prep. All three levels include OPP knowledge fluency.
Even though the subject matter and difficulty vary by level, these tips apply to all three levels of the COMLEX.
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Frequently asked questions
Can you take the USMLE in addition to COMLEX?
Yes, you can take the USMLE in addition to COMLEX-USA. Although COMLEX is required for DO students, and USMLE is required for MD students, a slight majority of DO students take the USMLE on top of the COMLEX in order to boost their residency application strength.
COMLEX alone is generally sufficient for primary care specialties or rural geographic regions. Taking the USMLE makes you a better candidate for competitive specialties or urban areas.
As an osteopathic student, you are still required to take the COMLEX for eventual licensure.
Is COMLEX similar to the USMLE?
COMLEX-USA is similar to the USMLE in certain ways:
Both assess foundational biomedical science and clinical knowledge. 80% of the tested material overlaps.
Both COMLEX Level 1 and USMLE Step 1 are graded as Pass/Fail, and the latter tests in both series are graded on a three-digit numerical scale.
Both series discontinued the second half of their second test during the pandemic: USMLE Step 2-CS (Clinical Skills) and COMLEX Level 2-PE (Performance Evaluation).
Both series are generally required for licensure, although different states may allow exceptions for both allopathic (MD) and osteopathic (DO) doctors.
However, there are differences between COMLEX and USMLE:
COMLEX focuses on osteopathic medical knowledge specific to DO training, such as osteopathic manipulative treatment (OMT).
The test formats differ significantly because USMLE is administered by the National Board of Medical Examiners (NBME), while COMLEX is administered by the National Board of Osteopathic Medical Examiners (NBOME). Yes, NBME and NBOME are completely distinct organizations with no formal connection.
COMLEX generally allows less time per question than USMLE while featuring more questions per exam block.
Opinions from our clients, our experts, and online forums generally indicate that the USMLE is very structured, while the COMLEX may contain more ambiguous questions.
Is COMLEX harder than the MCAT?
The COMLEX is generally considered harder than the MCAT for the following reasons:
While the MCAT tests foundational scientific and clinical knowledge, the COMLEX assesses more advanced clinical reasoning, pathology, pharmacology, and osteopathic knowledge.
All levels of COMLEX are taken after you’re already a medical student, so you are expected to have a much wider breadth of knowledge than when you took the MCAT before med school.
COMLEX generally packs more questions into just about the same amount of time that you had to complete the MCAT, making time management harder on the COMLEX. Moreover, with MCAT questions, it’s typically easy to understand what the test is asking, while it may be tougher to identify what COMLEX questions are actually asking of you.
Final thoughts
All three levels of COMLEX are tough, but there are several ways you can set yourself up for success, increase your odds of passing Level 1 and Level 3, boost your Level 2 scores as well as your residency matching odds, and maintain your mental health throughout the process.
About the Author
Dr. Shirag Shemmassian is the Founder of Shemmassian Academic Consulting and one of the world's foremost experts on medical school admissions. For over 20 years, he and his team have helped thousands of students get into medical school using his exclusive approach.
