The exact ASCP BOC requirement, what coursework counts, and how to fill the gap if you are short of fulfilling your MLS certification requirements.
| The short answer To sit for the ASCP Board of Certification Medical Laboratory Scientist exam, you need 16 semester hours of biology (or 24 quarter hours), and at least one of those semesters must be a microbiology course with a lab. You also need 16 semester hours of chemistry, but the focus of this article is the biology side. That requirement is set by the ASCP Board of Certification and applies to every U.S. eligibility route that uses a non-MLS bachelor’s degree as the qualifying credential. The microbiology semester is non-negotiable — you cannot substitute a general biology, cell biology, or virology course for it. |
If your school operates on semester credits, you need 16 semester hours of biology coursework. If your school operates on quarter credits, you need 24 quarter hours. The math behind the conversion is straightforward: 1 semester hour equals 1.5 quarter hours, so 16 × 1.5 = 24.
Most U.S. universities use the semester system, so the 16-credit number is the one you will see most often. If your transcript is from a quarter-system school (the University of California system, Stanford, the University of Washington, Northwestern, and several others), you can multiply your quarter hours by 0.667 to convert to semester hours, or use the ASCP’s preferred 24-quarter-hour threshold directly.
A standard 16-credit biology stack for an MLS applicant looks something like this:
| Course | Credits | Notes |
| General Biology I + II (with lab) | 6–8 | Foundation. Most programs take a two-semester sequence; some count it as 8 credits, others 6. |
| Anatomy & Physiology I + II (with lab) | 6–8 | Counts as biology credit at most institutions. Often required separately by employers regardless. |
| Microbiology (with lab) | 3–4 | Mandatory. ASCP requires this specific course by name. |
| Total range | 15–20 | Most applicants land at 16–18 credits with this combination. |
If your bachelor’s degree did not include all three of those course groups, you will likely fall short of 16 hours. That is the most common gap we see at PrereqCourses.com — and it is also the most fixable.
Not every course with the word “biology” in the title will count. The ASCP BOC and the laboratory programs that audit applications look for science courses with sufficient depth and a laboratory component. Here is a working table of what generally counts and what does not.
| Counts as biology credit | Usually does NOT count |
| General Biology I & II (BIO 101/102 or BIO 1107/1108) with lab | Biology for non-majors or “Concepts of Biology” survey courses without lab |
| Anatomy & Physiology I & II with lab | Human Biology general-education survey courses |
| Microbiology (general, medical, or clinical) with lab — required | Environmental Science or ecology courses without molecular/cellular biology depth |
| Cell Biology, Molecular Biology, Genetics (especially helpful for MLS preparation) | Botany or Zoology (counts at some institutions, but check before relying on it) |
| Immunology, Virology, Hematology, Pathophysiology | Nutrition or Food Science courses (these are typically allied health, not biology) |
| Biochemistry (note: this counts as chemistry, not biology, for ASCP purposes) | Psychology, kinesiology, or health science courses, even when biology-adjacent |
| Lab science courses completed within a NAACLS-, CAAHEP-, or ABHES-accredited program | Online lecture-only science courses with no lab component (varies by program — confirm with the lab director) |
| The biggest source of confusion: biochemistry Biochemistry frequently shows up in biology departments and even has “bio” in the name, but for ASCP eligibility purposes it counts toward your chemistry 16 hours, not your biology 16 hours. This trips up applicants every cycle. Plan your coursework with this distinction in mind — a biochemistry course is one of the two acceptable options for satisfying the chemistry-side organic-or-biochemistry requirement, but it does not move the needle on your biology total. |
Of all the rules in the MLS prerequisite structure, the microbiology requirement causes the most denied applications. Here is why.
The ASCP BOC explicitly names microbiology as a required course in every U.S. MLS eligibility route. It is not a “recommended” course or a “strongly preferred” course. Programs will look at your transcript specifically for a course titled Microbiology, General Microbiology, Medical Microbiology, or an equivalent, with a laboratory component. If it is not on your transcript, you are not eligible — no matter how many other biology credits you have accumulated.
This is why biology majors and pre-med graduates are often surprised to find themselves short. Many four-year biology programs treat microbiology as an upper-division elective rather than a core requirement, which means a student can graduate with a B.S. in biology and 30+ biology credits, yet still be ineligible for MLS certification because they took genetics or ecology instead of microbiology.
What does not count as a substitute: a general biology course with a microbiology unit, a virology-only course, a parasitology-only course, or an introductory “microbes and disease” lecture for non-majors. The course needs to be a stand-alone microbiology course with a laboratory component.
If you are reading this article, you probably already suspect you have a gap. Here is how to confirm it in three steps.
Not your unofficial advising audit, not your degree progress page — your actual official transcript. Course titles, credit values, and lab indicators are what programs and the ASCP BOC will use to evaluate your eligibility, and these sometimes differ from what shows up in advising tools.
For each course, write down the title exactly as it appears on the transcript, the credit value, and whether the credits are semester or quarter. Then sort them into biology, chemistry, and other.
Total your biology credits. If you are at 16 semester hours (24 quarter hours) or above, and one of those courses is a microbiology course with a lab, you meet the biology side of the prerequisite. If you are short on either count, you have a gap to fill.
| If your transcript is older than 5–10 years, read the fine print Some MLS bachelor’s programs require that science prerequisites be completed within the last 5, 7, or 10 years. Tarleton State University’s MLS program, for example, requires that science courses be no older than 7 years. The ASCP BOC itself does not impose an age limit on prerequisite coursework, but the academic program where you complete your clinical training may. Always check with the specific program you intend to apply to before assuming an old course will count. |
Here is what we see most often when applicants come to PrereqCourses.com after running the audit above.
This is the single most common gap. You have plenty of biology credits, but no microbiology course on your transcript. The fix is one course.
PrereqCourses.com offers a self-paced, fully online Microbiology with lab course through Upper Iowa University. It is regionally accredited, transfers to virtually any U.S. institution, and can be completed in as few as 4–8 weeks if you push the pace. For most career changers and applicants with a degree gap, this is the fastest single move that converts an ineligible profile into an eligible one.
If your biology total is at 8 or 12 credits, you need to add 4 to 8 more. Common combinations to close the gap:
Some applicants completed biology courses in a non-traditional format — community college lecture-only sections, online courses without labs, or international transcripts that do not document a lab component. The ASCP BOC and the academic programs that evaluate your application both expect a lab component for the science courses you submit. If your biology credits are lecture-only, you may need to retake key courses (microbiology especially) in a format that includes a documented lab. The Upper Iowa University courses delivered through PrereqCourses.com include lab components by design.
Meeting the ASCP BOC’s 16-credit minimum gets you eligible for the certification exam. It does not necessarily make you a strong applicant for the bachelor’s-completion or post-baccalaureate MLS programs that lead to the exam. Most NAACLS-accredited MLS programs prefer applicants who exceed the minimum — typically 20 to 24 biology credits with strong grades.
If you are competitive, prioritize these courses beyond the minimum:
We built PrereqCourses.com specifically for the situation you are probably in right now: you have a bachelor’s degree, you are working or have other commitments, and you need to add a few science courses to qualify for a healthcare program — without re-enrolling in a four-year university.
Every course is delivered through Upper Iowa University, a regionally accredited institution. Credits transfer to virtually every U.S. college and university. Courses are self-paced (no fixed weekly meetings, no class schedule), include lab components, and start every month so you do not have to wait for a traditional semester to begin.
Browse our full course catalog or contact our advising team if you want a quick audit of where you stand against the MLS prerequisite requirements.
The ASCP Board of Certification itself does not set an expiration date on prerequisite coursework. However, the NAACLS-accredited bachelor’s-completion programs that prepare you to sit for the exam often do — typically 5, 7, or 10 years. If your science courses are older than that, the program (not the ASCP) may require you to retake them. Always check the specific MLS program you plan to apply to before assuming credits transfer.
No. The ASCP BOC requires one semester of microbiology by name. Cell biology, virology, parasitology, general biology with a microbiology unit, and immunology are not acceptable substitutes. The course must be titled microbiology (or a clear equivalent like “general microbiology” or “medical microbiology”) and include a lab.
Yes, as long as the course is from a regionally or nationally accredited institution and includes a documented laboratory component. The ASCP BOC accepts online coursework on equal footing with in-person coursework. The lab component is what most applicants need to verify carefully — a lecture-only online microbiology course will not satisfy the requirement.
24 quarter hours of biology, including one quarter of microbiology with a lab. The conversion factor is 1 semester hour = 1.5 quarter hours, so 16 × 1.5 = 24.
No. For ASCP MLS eligibility, biochemistry counts toward your 16 chemistry hours, not your 16 biology hours. Plan accordingly — if you took biochemistry to satisfy a biology requirement at a previous program, it will not transfer the same way for ASCP purposes.
16 is the minimum to be eligible to sit for the exam. Most NAACLS-accredited MLS bachelor’s-completion programs prefer 20 to 24 biology credits and use the additional coursework to evaluate competitiveness. If you have only 16, you are eligible — but you may want to add a course or two if your application target is a competitive program.
If you are pursuing the MLT-to-MLS bridge route (Route 2 under the ASCP BOC eligibility structure), the biology requirement is reduced. You still need a bachelor’s degree, one semester of microbiology, 16 semester hours of chemistry including organic or biochemistry, plus two years of clinical experience. The full 16 biology hours are not separately required for this route — your MLT credential covers most of the biology side.
Through self-paced programs like PrereqCourses.com, a single course such as microbiology can be completed in 4 to 8 weeks if you study consistently. A full 8-credit gap (e.g., Anatomy & Physiology I + II) typically takes 3 to 6 months. Career changers who need to rebuild the entire 16 hours from scratch should plan on 6 to 12 months.
Almost always yes, because the courses are delivered through Upper Iowa University, which is a regionally accredited institution. Regional accreditation is the gold standard for credit transfer in the United States. That said, every program has its own evaluation process, so we recommend confirming with the specific MLS program you plan to apply to before enrolling.
If you have audited your transcript and identified a missing microbiology course, a shortage of biology credits, or a science course that needs a lab component, you can start a PrereqCourses.com course this month. Enrollment is rolling, courses are self-paced, and credits transfer to U.S. institutions through Upper Iowa University’s regional accreditation.
Visit PrereqCourses.com to see the full course catalog, or contact our advising team for a free transcript review against the ASCP MLS biology requirements.
About this guide
All ASCP eligibility requirements cited in this article are drawn from the ASCP Board of Certification’s published documentation. Eligibility rules are subject to change; always verify current requirements directly with the ASCP BOC at ascp.org/boc before applying. PrereqCourses.com is a service of Upper Iowa University, a regionally accredited institution.
