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Blast Cells, Whole Blood

Published: August 9, 2026Updated: August 17, 2026

A blood test that measures immature white blood cells, called blasts, circulating in the blood.

Quick summary

["Detecting blood blasts can help evaluate unusual blood-cell production and guide further evaluation."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
26446-5
Short code
Blasts NFr Bld
Synonyms
Blasts NFr Bld
Category
liver
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test counts or estimates immature white blood cells, known as blasts, in a sample of whole blood. Blasts are not normally present in substantial numbers in peripheral blood.

Why might I need this test?

A blood blast count may be ordered when a complete blood count shows unusual results, when there are concerns about a blood or bone marrow disorder, or when monitoring certain treatments. It is often interpreted alongside other blood counts, the blood smear, and medical history.

How is the test performed?

A blood sample is collected from a vein and examined by a laboratory. The laboratory may use an automated cell counter, microscopic review of a blood smear, or flow cytometry to identify and count blasts.

How do I prepare for the test?

No special preparation is usually required for a routine blood draw. Follow any instructions provided by your healthcare professional, and tell the laboratory if you recently had a bone marrow test, received a blood or marrow transplant, or took medicines that could affect blood-cell production.

Reference range

Adult: 10-40 U/LN/A

Specimen: whole-blood

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Blood blast count

Frequently asked questions

What are blast cells?
Blasts are immature blood cells that are not yet fully developed. They are generally found in the bone marrow and normally are not present in significant numbers in circulating blood.
Does a positive blast count mean I have leukemia?
No. Blood blasts can have several causes, and their presence alone does not establish leukemia. Your clinician will interpret the result with other blood tests, symptoms, and possibly a bone marrow examination.
Is this the same as a bone marrow biopsy?
No. This test examines a peripheral blood sample and counts circulating blasts. A bone marrow biopsy samples marrow tissue and is generally used when more detailed evaluation is needed.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy