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White Blood Cell Count (WBC) with Differential Analysis (Serum/Plasma Substance Concentration)

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

This test measures the total number of white blood cells (WBCs) in your blood and breaks down their types (neutrophils, lymphocytes, monocytes, eosinophils, and basophils).

Quick summary

["WBC counts help diagnose infections, inflammation, or immune system issues."]

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

Key facts at a glance

LOINC
10579-1
Short code
WBC # Smn
Synonyms
WBC # Smn
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
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

Your healthcare provider may order this test to check for infections, such as bacterial or viral illnesses, or to monitor conditions like autoimmune diseases, leukemia, or chronic infections. It can also help evaluate symptoms like fever, fatigue, or unexplained weight loss.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. If you’re on blood thinners, let your provider know before the test.

What the Test Results Mean

A high WBC count may indicate infection, inflammation, or stress, while a low count could signal immune problems or blood disorders. The differential helps identify which types of white blood cells are elevated or reduced.

Common Conditions Monitored

This test is often used to diagnose or track conditions like pneumonia, appendicitis, lupus, HIV, or cancer. It can also help assess how your body responds to treatments for these conditions.

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.

Clinical Significance

Short name

WBC with Differential

Frequently asked questions

What could cause abnormal results?
Abnormal WBC counts can result from infections (bacterial, viral, or fungal), autoimmune diseases, stress, or certain medications. A differential analysis helps pinpoint which cell types are affected, guiding further diagnosis.
How often should I get this test?
Frequency depends on your health condition. Some patients get it monthly, while others may need it only occasionally, such as before surgery or during routine check-ups.
Can diet or lifestyle affect this test?
Diet or stress may temporarily influence WBC counts, but it’s not a major factor in test results. Avoid heavy meals 2 hours before the test to ensure accurate results.
  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