ASCP Board of Certification
ASCP MLS
ASCP Board of Certification Medical Laboratory Scientist (MLS)
The certification for medical laboratory scientists who perform and interpret clinical lab tests; required for employment in most clinical laboratories.
Full program: 7 decks, 914 cards.
What's on the exam
ASCP BOC MLS Examination Content Guideline (revised June 9, 2026)
Blood Banking / Immunohematology
17–22%ABO and Rh blood groups · Antibody identification and screening · Compatibility testing and crossmatch · Transfusion reactions and components · Hemolytic disease of the newborn
Body Fluids and Urinalysis
5–10%Urine physical, chemical and microscopic · CSF and serous fluids · Renal function · Fecal and other body fluids
Chemistry
17–22%Carbohydrates, lipids and proteins · Enzymes and cardiac markers · Electrolytes and blood gases · Endocrinology and therapeutic drug monitoring · Instrumentation and QC
Hematology
17–22%RBC, WBC and platelet morphology · Anemias and hemoglobinopathies · Leukemias and WBC disorders · Coagulation and hemostasis · CBC and cell counts
Immunology / Serology
5–10%Antigen-antibody reactions · Autoimmune and hypersensitivity · Infectious disease serology · Complement and immunoglobulins
Microbiology
17–22%Bacteriology and identification · Antimicrobial susceptibility · Mycology, parasitology and virology · Specimen collection and culture · Gram stain and media
Laboratory Operations
5–10%Quality control and assurance · Laboratory safety · Lab math and method evaluation · Regulations (CLIA) and informatics
Frequently asked questions
How much does the ASCP MLS cost?
The ASCP MLS costs $260. Non-refundable application fee.
How long is the ASCP MLS and how many questions does it have?
100 questions — 2.5 hours.
What do you need to pass the ASCP MLS?
Scaled score of 400.
Can you retake the ASCP MLS?
After 30 days; up to five attempts.
What is the best way to study for the ASCP MLS?
Start from the official outline and your primary study materials: the exam is weighted by domain (Blood Banking / Immunohematology 17–22%, Body Fluids and Urinalysis 5–10%, Chemistry 17–22%, Hematology 17–22%, Immunology / Serology 5–10%, Microbiology 17–22%, Laboratory Operations 5–10%). Once you've learned the material, spaced-repetition flashcards organized by those domains are an efficient way to retain it and refresh it before test day.
Ready to prepare?
Our ASCP MLS — Medical Laboratory Scientist program is organized by this outline's domains and scheduled by spaced repetition, with a path from first card to test day.
Flashcards are a memory tool. Learn the material first, then use NoReread to retain it and refresh what you already know. It doesn't replace studying the subject.