Overview
The American Society for Clinical Pathology Board of Certification (ASCP BOC) certifies medical laboratory professionals. It is not a single exam: the BOC runs a family of certification exams, each leading to its own credential, such as Medical Laboratory Scientist (MLS), Medical Laboratory Technician (MLT), Phlebotomy Technician (PBT), Medical Laboratory Assistant (MLA), Specialist in Cytometry (SCYM), Specialist in Molecular Biology (SMB) and Diplomate in Medical Laboratory Immunology (DMLI). It also runs shorter qualification exams.
The BOC offers two families of credentials. For ASCP credentials the education does not have to be from the United States; for ASCPi credentials it must be equivalent to US education. Each family has its own eligibility rules, and where an MLS(ASCP) route needs clinical experience, it must be gained in a laboratory with US (CLIA or DoD) or JCI or ISO 15189 accreditation.
This page describes the common exam format and uses the MLS credential as the worked example. Check the page for your own credential for its eligibility routes, content guideline and fee.
Who can apply
Every credential has its own eligibility routes, combining education, training, certification and clinical experience. You choose one category and route when you apply, and it cannot be changed after you submit.
Worked example: MLS(ASCP). As listed in 2026, the routes include:
Route 1: a bachelor's degree from an accredited college or university, plus completion of a NAACLS-accredited Medical Laboratory Scientist program within the last 5 years.
Route 2: valid MLT(ASCP) certification, a bachelor's degree with 16 semester hours of biology (including microbiology) and 16 of chemistry (including organic chemistry or biochemistry), and 2 years of full-time clinical experience across the main laboratory areas within the last 5 years.
Route 4: the same degree and science coursework, plus 5 years of full-time clinical experience within the last 10 years.
Route 5: valid MLS(ASCPi) certification with a transcript evaluation showing a US-equivalent bachelor's degree and 5 years of clinical experience within the last 10 years.
Route 3, which relied on CLA(ASCP) certification, was discontinued on 1 January 2023. Experience must be in an acceptable laboratory and documented on the BOC's forms.
Exam pattern
| Feature | Detail |
|---|---|
| Delivery | Computer-based, at Pearson test centres |
| Question type | Multiple-choice, four options, one best answer |
| Most certification exams | 100 questions in 2 hours 30 minutes |
| DMLI | 150 questions in 4 hours |
| PBT | 80 questions in 2 hours |
| MLT for California state licensure only | 80 questions in 2 hours |
| Qualification exams | 50 questions in 90 minutes, non-adaptive |
| Scoring scale | 100 to 999; 400 is the minimum pass |
Most certification exams use computerised adaptive testing (CAT). The first question is close to the pass standard; a correct answer brings a slightly harder question and a wrong answer a slightly easier one. You cannot skip questions, but you can flag them and return if time remains. Questions from all content areas are mixed throughout, and some unscored field-test questions are included. The DMLI, MLA, SCYM and SMB exams are not adaptive.
Syllabus
Worked example: MLS. The content guideline sets these ranges of the exam:
| Content area | Share |
|---|---|
| Blood banking | 17 to 22% |
| Chemistry | 17 to 22% |
| Hematology | 17 to 22% |
| Microbiology | 17 to 22% |
| Urinalysis and other body fluids | 5 to 10% |
| Immunology | 5 to 10% |
| Laboratory operations | 5 to 10% |
Questions may be theoretical or procedural, and regulatory questions are based on US sources such as the FDA and CLIA. Each credential has its own content guideline and reading list on the BOC site.
Marking and results
A preliminary pass or fail appears on screen at the end of the exam. Within four business days, provided your transcripts have been received and processed, you get an email to log in and view your official score report. It shows pass or fail and a scaled score from 100 to 999, with 400 needed to pass. There is no fixed number or percentage of correct answers needed, because CAT scoring uses the pattern of responses.
A failed score report breaks the result down by subtest area to guide further study. Passing reports do not include a breakdown.
Fees
As listed on the BOC site in 2026, the non-refundable application fee for MLS is US$260. Fees differ by credential, and reduced pricing exists for candidates educated and living in low- and middle-income countries. Every new application carries a new fee.
How to apply
Check the eligibility routes for your credential and decide between ASCP and ASCPi.
Gather the required transcript or transcript evaluation and experience or training forms before applying.
Submit the online application with the fee.
Once approved, schedule your exam with Pearson.
After the exam
New credential holders receive a digital badge through Credly from January 2026; wall certificates are no longer issued. Credentials are kept current through the BOC's Credential Maintenance Program (CMP).
If you fail, you can apply again after viewing your official score report. You may take an exam five times under one eligibility route while you still meet its requirements; after five failed attempts you must qualify under another route. Your new eligibility period starts no earlier than 30 days after your previous exam.
Preparation tips
Download the content guideline for your credential and plan study time by its percentages.
Use the BOC reading list for your credential.
Answer every question carefully: CAT does not reward deliberately missing questions, and you cannot go back to skipped items.
What score do I need to pass an ASCP BOC exam?
Scores run from 100 to 999, and 400 is the minimum passing score.
How many times can I take an ASCP BOC exam?
Five times under one eligibility route, with at least 30 days between attempts. After that you must qualify under a different route.
Is ASCP one exam?
No. The ASCP Board of Certification runs separate exams for each credential, such as MLS, MLT and PBT.