White Blood Cell Count (Serum/Plasma Substance Concentration)
This test measures the concentration of white blood cells in a blood sample, often performed to assess immune function or detect infections.
["White blood cells help fight infections and protect your body from illness."]
Key facts at a glance
- LOINC
- 26469-7
- Short code
- WBC # Snv
- Synonyms
- WBC # Snv
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile tube
- 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
- 2-5 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h
- Hemolysis max
- 300
- TAT
- 4–24 hours
- Order
- routine
Why Might You Need This Test?
Your doctor may order this test to check for signs of infection, inflammation, immune disorders, or other health conditions affecting your white blood cell levels. It can also be used during cancer treatments or to monitor recovery from surgery.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves drawing blood from a vein, but this is less common for this specific test. Avoid strenuous activity or medications that could affect results.
How the Test Is Performed
A healthcare provider will take a blood sample from a vein in your arm using a small needle. The blood is then sent to a lab for analysis. The test measures the total number of white blood cells in your serum or plasma.
What the Results Mean
Results are typically reported as a count of white blood cells per microliter (cells/µL). While reference ranges vary by lab, abnormal results may indicate low (leukopenia) or high (leukocytosis) white blood cell counts, which can signal infections, autoimmune diseases, or other health concerns.
Reference range
Adult: 4.5-11.0 x 10^9/LN/A
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 (Serum/Plasma)
Frequently asked questions
What Are Common Causes of Abnormal Results?
How Often Should I Get This Test?
Can I Eat or Drink Before This Test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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