LatticeMLS has a free 10-question MLS sample that needs no account. A free account opens about 700 practice questions in every examination area and a timed 100-question mock. Every question has a written explanation, shown once your answer is final.
What to look for
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| Look for | Why it helps |
|---|---|
| Four options, one best answer | ASCP BOC examination questions have a stem and four options with one correct answer. |
| Questions at several levels | ASCP BOC questions range from recall to comprehension to application or analysis. A set of recall questions alone leaves out the other two levels. |
| Results to read and calculations to work | The MLS guideline says questions measure the skills to apply knowledge, calculate results, correlate patient results with disease states and follow quality assurance protocols. |
| An explanation for every question | It shows why the answer is right and why each other option is wrong. |
| Coverage that follows the current weights | Blood Banking, Chemistry, Hematology and Microbiology are 17 to 22% each. Immunology, Laboratory Operations, and Urinalysis and Other Body Fluids are 5 to 10% each. |
| Results by area | They show which area to study next. |
How LatticeMLS questions work
- Levels 1 to 5. Each question has a level: recall one fact, use one fact in a simple case, read results or work a calculation, put several findings together, and explain findings that seem to disagree. A learner right at the simulated standard answers about 8 in 10 level 1 questions correctly and about 1 in 10 level 5 questions.
- Difficulty from learner answers. An editor gives each question a starting difficulty. Anonymous answers from timed mocks and adaptive exams then adjust it.
- Feedback that points to a lesson. After each practice answer you see Correct or Incorrect, the answer letter, the explanation and a link to the lesson section that teaches it.
- New questions in every mock. Mocks draw from a separate pool, so each mock question is one you have not seen in practice or daily review.
Example questions
Both come from question levels, which has an example at every level in every area.
A calculation in hematology (level 3)
An adult's hematocrit is 33% and the red cell count is 5.50 × 10⁶/µL. What is the MCV?
- A. 6.0 fL
- B. 16.7 fL
- C. 60.0 fL
- D. 181.5 fL
Each wrong option comes from a setup error. Option A leaves out the final multiplication by 10. Option B divides the red cell count by the hematocrit as a fraction (5.50 ÷ 0.33). Option D multiplies the two values. Writing the formula with units first catches all three.
Results that point to a specimen problem in chemistry (level 4)
An outpatient with no symptoms has these results. Yesterday the potassium was 4.1 mmol/L. The hemolysis index is within limits.
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| Test | Result |
|---|---|
| Potassium | 7.6 mmol/L |
| Calcium | 3.9 mg/dL |
| Creatinine | 0.9 mg/dL |
What is the most likely explanation?
- A. In vitro hemolysis
- B. Acute kidney failure
- C. A delay in separating the specimen
- D. Contamination with potassium EDTA
A delay in separating the specimen can also raise potassium. It does not lower calcium.
Try the free sample
Open exam practice and start the free sample. Today's set follows the MLS blueprint and changes each day.
- Answer each question before you read the explanation.
- Read the explanation for every miss and every lucky guess.
- Write down the subject and the reason for each miss.
- With a free account, follow up with a set of 10 or 25 questions in your weakest area.
For a full study schedule, see How to Study for the ASCP MLS Exam. To sit the examination again, see the ASCP MLS exam retake plan.
Official ASCP BOC materials
ASCP BOC publishes the MLS content guideline and a reading list for free. Check for a newer guideline as your examination date approaches. ASCP also sells the BOC Study Guide, the BOC Interactive Practice Exam, the Quick Compendium of Medical Laboratory Sciences and the MLS Online Review Course.3,4
References
- American Society for Clinical Pathology Board of Certification. About the examination. Accessed November 1, 2026. ASCP BOC: About the Examination. Back to text
- American Society for Clinical Pathology Board of Certification. Medical Laboratory Scientist, MLS(ASCP) and MLS(ASCPi) Examination Content Guideline. Revised June 9, 2026. Accessed November 1, 2026. ASCP BOC MLS content guideline. Back to text
- American Society for Clinical Pathology Board of Certification. Content guidelines and reading lists. Accessed November 1, 2026. ASCP BOC: Content Guidelines and Reading Lists. Back to text
- American Society for Clinical Pathology. BOC exam prep from ASCP. Accessed November 1, 2026. ASCP: BOC Exam Prep. Back to text