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Blasts, Number per Liter

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

Measures the number of blast cells, which are immature blood-forming cells, in a laboratory specimen.

Quick summary

["An increased blast count may indicate a blood-forming disorder and should be interpreted by a healthcare professional."]

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

Key facts at a glance

LOINC
33373-2
Short code
Blasts NFr Plr
Synonyms
Blasts NFr Plr
Category
liver
Sample
fluid
Container
Sterile tube
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
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

What is this test?

This test counts immature blood-forming cells called blasts in a specimen. Blasts can develop into healthy blood cells, but larger numbers may be associated with abnormal blood-cell production.

Why might I need this test?

A blast count may help evaluate unexplained anemia, infection, or abnormal blood-cell results. It may also be used to monitor a person with a blood disorder or during treatment for leukemia.

How is the test performed?

A laboratory instrument counts the blasts in the specimen. When needed, a specialist may review the cells using microscopy or flow cytometry to help identify them more accurately.

How do I prepare for the test?

If the test is performed on blood, fasting is usually not required. If another specimen is requested, follow the specific collection instructions provided by your healthcare professional.

Reference range

Adult: 10-40 U/LN/A

Specimen: fluid

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

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Blasts are normally absent or present at very low levels, although expected values can vary by specimen and laboratory. An increased count may occur with leukemia, other bone-marrow disorders, severe infection, or treatment effects. The result must be interpreted with other blood tests, symptoms, and sometimes bone-marrow testing because it does not establish a diagnosis by itself.

Short name

Blast Count

Frequently asked questions

What are blast cells?
Blasts are immature cells produced in the bone marrow as blood cells develop. Most healthy people have very few circulating blasts.
Does an abnormal blast count mean someone has leukemia?
Not necessarily. An elevated count can have several causes, including infection, marrow disorders, and treatment effects, so additional testing may be needed.
Is fasting required for a blast count?
Fasting is generally not required for a blood-based blast count. Preparation can differ if the test is performed on another specimen, so follow your clinician's instructions.
  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