Whether you’re deciding between the MD or DO route for your medical school experience, you’re probably already thinking about exam requirements. While the USMLE Step exams (MD) and COMLEX Level exams (DO) serve a similar purpose, they have different timelines that may influence your decision.

While we’ve already covered the USMLE exam timeline, let’s break down the COMLEX exam timeline.



The Level 1 COMLEX exam is a standard basic sciences exam. Students are tested on their understanding of the biomedical sciences and health maintenance knowledge. Complex Level 1 is typically taken in the spring of a student’s second year of medical school, placing it slightly earlier than MD students might take their first USMLE exam.

The summer after the first year is a good time to begin studying for COMLEX Level 1.


COMLEX Level 2

After taking Level 1, students will begin preparing for clinicals in their third year of med school. Throughout clinicals, students are preparing for the COMLEX Level 2 CE exam. The Level 2 exam was reduced to just a single exam after the Level 2 PE exam was permanently discontinued in June 2022.

Typically taken in the summer between Year 3 and Year 4, COMLEX Level 2 tests students’ clinical skills application across six disciplines:

  • Family Medicine
  • Emergency Medicine
  • Internal Medicine
  • Pediatrics
  • Osteopathic Principles and Practice
  • Psychiatry
  • Surgery


COMLEX Level 3

At two days, Level 3 is the longest of the COMLEX exams. However, this exam is typically taken after graduating from med school but before the end of a student’s first year of residency.

The COMLEX Level 3 exam covers competency in medical areas such as osteopathic knowledge, patient care, ethics, and more.

Passing COMLEX Level 3 is the final key to practicing osteopathic medicine unsupervised. It represents a student’s medical competency and proves the ability to deliver safe, quality, ethical healthcare.

It is, also, the end of a long and arduous exam timeline.