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Leukocyte Differential Count, Blood

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

A blood test that measures the different types of white blood cells and their relative proportions. It is often included as part of a complete blood count.

Quick summary

["The differential helps identify the likely cause of infection, inflammation, or other changes in blood-cell production."]

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

Key facts at a glance

LOINC
28405-9
Short code
LOSINGMYLOOKSISDEVASTATING
Synonyms
—
Category
liver
Sample
serum
Container
Red-top tube (SST)
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
Method
reported-living-hiv
CPT
84484
SNOMED
302774002
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

What is this test?

A leukocyte differential counts the main types of white blood cells in your blood, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. It may also report immature cells, depending on the laboratory method.

Why might I need this test?

Your clinician may order this test to evaluate infection, inflammation, allergies, medication effects, or unexplained changes in blood-cell counts. It is commonly used with other tests to help interpret a complete blood count.

How is the test performed?

A blood sample is analyzed by an automated cell counter, and a microscope review may be performed to confirm the results or examine unusual cells. No special procedure is usually required beyond the routine blood draw.

How do I prepare for the test?

Fasting is generally not required for a complete blood count with differential. Follow any instructions from your clinician, and tell the laboratory about medicines or recent illness that could affect your results.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

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

White blood cell differential

Frequently asked questions

Is a white blood cell differential the same as a complete blood count?
It is often part of a complete blood count. The differential focuses on the types and proportions of white blood cells, while the complete blood count also measures red blood cells, hemoglobin, hematocrit, and platelets.
Does this test diagnose an infection on its own?
No. The pattern of white blood cells can provide clues about the type or severity of illness, but it must be interpreted with symptoms, examination findings, and other laboratory tests.
Can medicines or other conditions change the results?
Yes. Steroids, chemotherapy, some other medicines, recent infections, allergies, and several chronic conditions can affect white blood cell counts.
  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