White Blood Cell Count (Peripheral Blood)
This test measures the number of white blood cells in a sample of your blood. White blood cells help protect your body from infections and diseases.
["Your doctor may order this test to check for infections, immune system issues, or other health conditions."]
Key facts at a glance
- LOINC
- 49498-9
- Short code
- WBC # Bld Est
- Synonyms
- WBC # Bld Est
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- 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
- estimate
- CPT
- 85004
- SNOMED
- 900000000000003002
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Doctors may perform a white blood cell count to diagnose or monitor conditions such as infections (like pneumonia or urinary tract infections), autoimmune diseases (like lupus or rheumatoid arthritis), blood disorders (like leukemia), or to check for signs of inflammation in your body. It can also be used during pregnancy to monitor fetal health or after certain treatments.
What to Expect Before the Test
No special preparation is needed for this test. You may have a small needle inserted into your arm or hand to draw blood. If you’re nervous, let your healthcare provider know—they can help make the process more comfortable.
What the Results Mean
The test result shows your total white blood cell count. A higher-than-normal count may indicate an infection, inflammation, or other medical conditions. A lower-than-normal count could suggest immune system problems or blood disorders. Your doctor will interpret the results in the context of your overall health and symptoms.
Common Conditions Monitored
This test is often used to track conditions like chronic infections, cancer (such as leukemia), or immune deficiencies. It may also be checked regularly if you have a history of frequent infections or certain chronic illnesses.
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
Frequently asked questions
What might cause an elevated white blood cell count?
What might cause a decreased white blood cell count?
How often should this test be repeated?
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