Immune and inflammation
White blood cell count (WBC)
WBC, leukocytes
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Compare membershipsWhat your white cell count says about your immune system.
Your white blood cell count is the total number of immune cells in a set volume of blood. It helps assess infection, inflammation, and bone marrow function, and a related test called the differential breaks it down into five cell types.
Everyday factors can nudge your count.
White cell counts respond quickly to what's happening in your body. Smoking, emotional or physical stress, vigorous exercise, pregnancy, and medications such as corticosteroids can all raise the count without any infection present.
A low count can follow a viral illness or certain medications, and some healthy people naturally run a little below the reference range. Counts that stay low or high, or that change sharply, are worth a closer look with a clinician.
One result is a snapshot. A trend tells you more.
Questions
Should I get tested while I'm sick?
If you're unwell or just getting over an infection, your white cell count may reflect that illness. Testing when you feel well gives a better picture of your usual baseline.
Which white cell types are measured?
The differential reports neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each plays a different role, so the pattern across them often says more than the total.