What is a WBC Count Test?
A blood test that measures the number of white blood cells in your blood, which are essential for fighting infections and protecting your immune system.
{"WBC count measures your body's ability to fight infections","Normal range is typically 4-11 x 10^9/L","High levels may indicate infection, inflammation, or leukemia","Low levels may suggest bone marrow problems or autoimmune diseases","The test requires a simple blood draw"}
Key facts at a glance
- LOINC
- 6690-2
- Short code
- WBC
- Synonyms
- —
- Category
- hematology
- Sample
- whole-blood
- Container
- Lavender Top Tube (EDTA)
- Units
- 10^9/L
- Ref low
- 4
- Ref high
- 11
- Critical range
- 2 10^9/L – 30 10^9/L
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- flow-cytometry
- CPT
- 85048
- SNOMED
- 86181001
- Specimen volume
- 2-3 mL of whole blood
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 72 hours. Do not freeze. Mix tube gently by inversion 8-10 times immediately after collection.
- Hemolysis max
- 50
- Lipemia max
- 50
- Icterus max
- 20
- TAT
- 1–3 hours
What is a WBC Count Test?
A White Blood Cell (WBC) count is a common blood test that measures the number of white blood cells in a sample of your blood. White blood cells, also called leukocytes, are a crucial part of your immune system. They help your body defend against infections, bacteria, viruses, and other harmful invaders.
Why is this Test Performed?
Your healthcare provider may order a WBC count as part of a routine complete blood count (CBC) or when you have symptoms such as fever, fatigue, or signs of infection. The test helps doctors evaluate your overall immune system function and detect conditions that affect white blood cell production or destruction.
How is the Test Done?
A healthcare professional will draw a small sample of blood from a vein in your arm using a needle. The sample is then sent to a laboratory for analysis. The procedure only takes a few minutes and is generally well-tolerated with minimal discomfort.
Understanding Your Results
Normal WBC count typically ranges from 4 to 11 x 10^9/L (billions of cells per liter of blood). However, normal ranges may vary slightly depending on the laboratory and your individual factors such as age, sex, and overall health. Your doctor will interpret your results in the context of your specific situation.
Reference range
Adults: 4.5-11.0 x 10^9/L. Reference ranges may vary by laboratory and patient population (neonates, pediatric).10^9/L
No fasting required. Inform laboratory of current medications including corticosteroids, chemotherapy agents, and immunosuppressants as these may affect results. Recent strenuous exercise may transiently elevate WBC.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated WBC count (leukocytosis) may indicate bacterial infections, inflammatory conditions (such as rheumatoid arthritis), tissue damage (from burns or surgery), leukemia, or allergic reactions. Certain medications like corticosteroids can also increase WBC levels.
Low WBC count (leukopenia) may result from viral infections, bone marrow disorders, autoimmune diseases, certain medications (like chemotherapy), or nutritional deficiencies. A low count can increase your risk of infections.
The WBC count is often used alongside other blood tests to help diagnose and monitor conditions affecting the blood and immune system. Your doctor may order additional tests, such as a differential WBC count, to examine the different types of white blood cells.
Short name
WBC
Part of panels
Frequently asked questions
Do I need to fast before a WBC test?
Are there any risks from the blood test?
What can affect my WBC count?
How often should I have my WBC count checked?
What happens if my WBC count is abnormal?
Sources
- 1
- 2
- 3LOINC Code ReferenceSource
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 10, 2026. · Read our editorial policy