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White Blood Cell Count (Manual Differential)

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

This test measures the total number of white blood cells in your blood and helps identify types of cells that may indicate infections, inflammation, or other health conditions.

Quick summary

["This test helps doctors diagnose and monitor blood-related disorders."]

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

Key facts at a glance

LOINC
812-8
Short code
WBC # Smn Manual
Synonyms
WBC # Smn Manual
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
4.5
Ref high
11
Critical range
2 N/A – 30 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
CPT
85004
SNOMED
900000000000003002
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 check for infections, such as bacterial or viral illnesses, or to evaluate conditions like leukemia, lymphoma, or autoimmune diseases. It can also help monitor chronic conditions like HIV or certain types of anemia.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re nervous, let your doctor or phlebotomist know—they can help make the process more comfortable.

What Happens During the Test

A healthcare professional will take a small sample of blood from a vein in your arm. The blood is then examined under a microscope by a trained technician to count and identify different types of white blood cells manually.

What the Results Mean

Results show the total white blood cell count and the proportions of different cell types (e.g., neutrophils, lymphocytes, monocytes). Abnormal counts may signal infections, immune disorders, or other health issues that need further investigation.

Reference range

Adult: 4.5-11.0 x 10^9/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

WBC Count (Manual Diff)

Frequently asked questions

What causes white blood cell counts to be high?
High white blood cell counts can result from infections (like colds or flu), inflammation, stress, or certain medications. Chronic conditions like autoimmune diseases or cancers may also affect these levels.
What causes white blood cell counts to be low?
Low white blood cell counts can occur due to infections, bone marrow disorders, certain medications, or immune system conditions. Severe cases may increase the risk of infections.
How often should I get this test?
Your doctor will determine how often you need this test based on your health condition, symptoms, or treatment plan. Regular monitoring may be needed if you have chronic illnesses or undergo treatments that affect your immune system.
  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