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Flow Cytometry (for Leukocyte Differential Count)

Published: August 9, 2026Updated: August 16, 2026

This test measures the types and proportions of white blood cells in your blood, often used to assess immune function or diagnose conditions like infections or blood disorders.

Quick summary

["Helps doctors understand your immune system’s balance of white blood cells."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
89238-0
Short code
OB Flowsheet
Synonyms
OB Flowsheet
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
obstetrics
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test to evaluate immune responses, check for infections, monitor blood disorders (like leukemia), or assess conditions affecting white blood cell counts, such as autoimmune diseases or chemotherapy side effects.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein for blood collection, similar to other blood tests. If you’re on blood-thinning medication, let your doctor know.

What the Results Mean

Results show the percentage of different white blood cell types (e.g., neutrophils, lymphocytes, monocytes). Abnormal counts may indicate infections, inflammation, or blood-related disorders.

Common Conditions Monitored

This test helps diagnose or monitor conditions like chronic infections, immune deficiencies, blood cancers, or reactions to treatments that affect white blood cells.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Flow Cytometry Leukocyte Count

Frequently asked questions

Will this test affect my medications?
This test itself doesn’t directly interact with medications, but doctors may adjust treatments if your white blood cell counts are low or high due to the test results.
How often will I need this test?
Frequency depends on your health condition. Some patients need it monthly, while others may only require it once or twice a year.
Can I eat or drink before this test?
You can eat and drink normally unless your doctor specifies otherwise. No fasting is required for this test.
  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 16, 2026. · Read our editorial policy