Medical School USMLE Step 1

COMLEX Level 1 vs. USMLE Step 1: Differences and Preparation

Ever wonder what the differences are between the USMLE Step 1 and the COMLEX Level 1 exam? Read on to find out.

If you are an osteopathic medical student, then you may have heard about two medical licensing exams: the Comprehensive Osteopathic Medical Licensing Examination (COMLEX) Level 1, as well as the United States Medical Licensing Examination (USMLE) Step 1. In a nutshell, the COMLEX Level 1 is the osteopathic equivalent of the USMLE Step 1 for allopathic students, although there are important differences between the two exams. In this post, I’ll summarize the differences between the COMLEX and USMLE exams.

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Summary: Differences between COMLEX Level 1 and USMLE Step 1

The following table summarizes the differences between the COMLEX Level 1 and the USMLE Step 1 exams.

USMLE Step 1 COMLEX Level 1
Cost (as of 2019) $630 [NBME] $660 [NBOME]
Recognized by Residency Programs Yes Yes [NBOME]
Number of Questions 280 (7 blocks of 40) 400 (8 blocks of 50)
Total Test Time 8 hours 9 hours
Time per Block 60 minutes Self-paced (~60 minutes)
Tutorial Time 15 minutes 10 minutes
Authorized Break Time 45 minutes (self-scheduled) 60 minutes (two 10-minute breaks & 40-minute lunch)
Passing Score 194 400
Practice Exams/Self Assessments NBME – reviewable NBOME – unable to review
Lab Values  Provided in attachment Embedded in questions


The costs of the two exams is roughly comparable, at $630 for the USMLE Step 1 [NBME] and $660 for the COMLEX Level 1 [NBOME].

Recognition by Residency Programs

comlex vs usmle
There still are differences in recognition of the COMLEX and USMLE exams by residency programs.

In November of 2018, the American Medical Association approved a resolution recognizing the equivalency of the COMLEX and the USMLE exams for residency applications [AMA]. With the merger of the American Osteopathic Association [AOA] into the Accreditation Council for Graduate Medical Education [ACGME] in 2020, there will be a single accreditation group for all MD and DO programs, with the goal of ensuring equivalence for residency applications [AAMC]. However, it is undeniable that in the current day, USMLE exams are still largely preferred by most ACGME-accredited residency programs. Even with the merger, this will take time to change. According to the American Association of Colleges of Osteopathic Medicine:

The single GME accreditation system is not expected to reduce acceptance of the COMLEX-USA for residency admissions, but rather to continue to grow acceptance with the goal of one day achieving universal acceptance. However, it is likely – at least for a while – that some ACGME programs will continue to prefer to receive a USMLE score. If a student has aspirations for such programs, then that student will have to make the decision about whether to take the USMLE in addition to the COMLEX-USA.[AACOM].

Therefore, it is highly likely that for now, most DO students who want to be competitive for all ACGME programs will still need to take both the COMLEX Level 1 and the USMLE Step 1 exams.

Topic/Subject matter

comlex vs usmle topic differences
The COMLEX Level 1 emphasizes osteopathic practice essentials and musculoskeletal systems more than the USMLE Step 1.

While both exams have many areas of content that overlap, the COMLEX Level 1 has several differences compared to the USMLE Step 1 exam (Content outlines for the USMLE Step 1 and COMLEX Level 1 are freely available to view.). One of the differences is the inclusion of a “Osteopathic Principles, Practice, and Manipulative Treatment” section that makes up at least 11% of the COMLEX Level 1 exam [NBOME]. This includes, but is not limited to, the following: Chapman reflexes, viscerosomatic relationships, and how to appropriately code for osteopathic manipulative therapy (OMT). Other important unique sections to the COMLEX Level 1 exam are the following sections: “Osteopathic Patient Care and Procedural Skills”, “Practice-Based Learning and Improvement in Osteopathic Medical Practice”, “Interpersonal and Communication Skills in the Practice of Osteopathic Medicine”, and “Professionalism in the Practice of Osteopathic Medicine”. These sections are difficult because they require application of concepts, rather than pure recall of details. The four osteopathic tenets are also tested under those topics. Examples of questions under those topics are determining the next appropriate clinical action, identify the ethical principle being applied, the next best step for advising the patient, the best response to an ethical dilemma, questions on human development, and the best management decision based on limited evidence or unfamiliar data. And while those topics are not necessarily “high yield”, it is still important to learn and understand not only for the boards, but also for the rest of your career as an osteopathic physician.

Apart from the osteopathic practice elements above, both exams assess essentially the same subject matter: the knowledge base any physician should know. What differs is that certain subjects are given more weight on the COMLEX Level 1 as opposed to the USMLE Step 1. Based on the information available on both the NBME and NBOME websites, the following differences are notable: COMLEX Level 1 has a greater emphasis on the Musculoskeletal System (at least 13%) whereas Step 1 allocates a lower percentage (at least 6-10%). Also, the COMLEX Level 1 states that the “Respiratory System” makes up at least 10% of subject matter and “Genitourinary/Renal System and Breasts” at least 5% on the exam. In contrast, the USMLE Step 1 groups “Respiratory & Renal/Urinary Systems” into a section composing about 9-13% of the test. 

Additionally, the way in which questions are worded can be different between the exams. My personal experience of taking both exams was that the USMLE Step 1 questions felt more detailed, with a clearly defined learning objective or set of clues needed to reach the correct answer. On the other hand, the COMLEX Level 1’s question wording was more vague and clinically-oriented, and required more open creative thinking. Again, that is just my personal experience and everyone else’s experience will be different. 

The best way to get used to the wording of each exam is to take the official practice exams. Official practice exams for USMLE Step 1 can be found here. Official practice exams for COMLEX Level 1 can be found here

Number of Questions and Questions per Block

The COMLEX Level 1 has 400 questions in total (8 blocks of 50 questions), whereas the USMLE Step 1 has 280 questions (7 blocks of ~40 questions). In total, this means that the COMLEX Level 1 has 120 more questions than USMLE Step 1. However, a block for Step 1 is much different from a block in Level 1. This will be explained below.

Timing of Blocks

comlex vs usmle timing
The time allotted per block differs between the two exams.

The major difference of the blocks between both exams is that each block on the USMLE Step 1 has its own set timer of 60 minutes. Once 60 minutes for that block has elapsed, then you automatically move on to the next block. But on the COMLEX Level 1, the timer is not as simple. Instead of designating 60 minutes per block, it gives 4 hours for the first 4 blocks in the morning, then another 4 hours for the remaining blocks in the afternoon. The timer starts at 4 hours and it is up to you how you want to pace yourself for those 4 blocks. So for example, you can take 1.5 hours for the first block, but that means you have have 2.5 hours to complete 3 more blocks. Or you can take 65 minutes for the first block and then time yourself for the remaining 3 blocks. 

Break Times

comlex vs usmle break time

Break times are a key difference between the COMLEX Level 1 and the USMLE Step 1.

For the USMLE Step 1, there is a 45-minute scheduled break time. You can add on additional time by skipping the 15-minute optional tutorial, giving you a total of 60 minutes. You are able to control how you use and allocate break time yourself on the USMLE Step 1. For example, after the first block you can take a 7-minute break. Then for the second block, you can take a 3 minute break. That would leave 35 more minutes of authorized break time remaining and if you skipped the tutorial, 50 minutes remaining. However, when you take your break, keep in mind that the timer is always ticking down. It takes time to check in and out through security, so your chosen “10-minute” break can feel more rushed than you think. 

For the COMLEX Level 1, the break times are predefined and chosen for you. You get 60 total minutes of total break time, broken down as follows: After the first two sections, you will have a 10-minute break. After another two sections (four sections total), you will be allotted a 40-minute lunch break. Complete two more sections, and you’ve earned another 10-minute break, before you finish with the last two sections. In short, you generally need to complete two sections before a predefined “authorized” break, which is always 10 minutes except for a 40-minute lunch break in the middle of the exam. 

Though many advise that you skip the tutorial altogether on Step 1 and thus, add on more time to your break, it’s not a bad idea to spend about 5 minutes of the tutorial in getting familiar with the exam interface. Even though the practice question banks in the market do their best to replicate what the exam layout will look like, it is not the exact same thing and the actual exam layout will have additional features. One great example is that if you skip the tutorial for COMLEX Level 1, you will not realize that for the audio portions of the exam, you have to make sure you stop any audio sounds yourself. Otherwise you are going to hear heart sounds for the entire test. I personally don’t exactly recall if skipping the COMLEX Level 1 tutorial added any break time, so there may not be any time advantage in skipping the COMLEX Level 1 tutorial. 

Passing Score

The passing score for the USMLE Step 1 and COMLEX Level 1 exams changes every year. Generally speaking, the passing scores are 194 for USMLE Step 1 and 400 for the COMLEX Level 1.

Official Practice Exams

comlex vs usmle practice exams
The official practice exams or self-assessments administered vary greatly between the NBME and NBOME.

The NBME administers the USMLE Step 1 and the NBOME administers the COMLEX Level 1.  They both provide official practice exams on their websites, albeit at a cost. The NBME provides the Comprehensive Basic Science Self-Assessment (CBSSA) for $60 per exam. The NBOME provides the Comprehensive Osteopathic Medical Self-Assessment Examination (COMSAE) for $60 per exam. If you are a DO student, try asking your school to purchase additional COMSAE exams for you to practice with in order to prepare for your COMLEX Level 1. That can help save on costs. Also know that as a DO student, your school will have you sit for an official COMSAE exam before allowing you to take the COMLEX Level 1. Each osteopathic school will have different passing scores for their students. Generally, if you don’t meet your school’s passing score, you will have to take as many COMSAE exams as needed to meet the requirement. Only then, will you be able to sit for the COMLEX Level 1.

An important difference between the official practice exams is the NBME exams save your answers and are therefore reviewable: you can see where you made mistakes in your practice assessment. In contrast, the NBOME practice exams simply give you the test without saving answers and will only provide a breakdown at the practice exam’s conclusion. As such, they are not reviewable.

Lab Values

Lab values on the USMLE Step 1 are often included in question stems, but normal values or reference ranges are accessed via an attachment that is shown in a separate window. It is generally a good idea to get familiar with the general locations of common lab values (basic metabolic panel, blood counts, etc.) so you’re not wasting valuable time looking for a normal range on test day. Memorizing the normal ranges is even better. In contrast, the COMLEX Level 1 embeds all normal ranges directly within the question stem, so there is no need to look elsewhere for a normal range. However, there is no attachment of other lab values. 


In conclusion, there are significant differences between the USMLE Step 1 and the COMLEX Level 1 that all DO students should know. They involve both the subject matter and the specific exam format, so be sure to know them before test day!

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