White Blood Cell Count
Also written as: WBC, Leukocyte count
The number of infection-fighting cells in a volume of blood.
What it measures
The total number of white blood cells in a given volume of blood. White cells are the immune system cells that respond to infection, injury, and inflammation.
Why a doctor orders it
It is part of nearly every routine CBC. A clinician may look at it more closely when infection, inflammation, or a problem with the bone marrow is being considered, or to monitor a treatment known to affect blood counts.
What is generally associated with a higher result
A raised white cell count is broadly associated with the body responding to something - bacterial or viral infection, inflammation, tissue injury, physical or emotional stress, smoking, and certain medications, particularly corticosteroids. Marked elevations can also occur in disorders of the bone marrow.
What is generally associated with a lower result
A reduced count is broadly associated with some viral infections, certain autoimmune conditions, some vitamin deficiencies, several medications including chemotherapy, and conditions affecting the bone marrow.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Recent infection, even a mild one that has resolved
- Corticosteroids and some other common medications
- Strenuous exercise shortly before the draw
- Pregnancy
- Smoking
Questions to take to your appointment
- Is this result different from my previous ones?
- Could any medication I take be affecting this?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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