Quick Guide: White blood cell (WBC) count Blood Test
What it is: A white blood cell (WBC) count measures the total number of white blood cells in a blood sample, typically as part of a complete blood count.
Why it's ordered: Ordered alongside a CBC to help evaluate infection, inflammation, allergic reaction, or blood disorders, or as part of routine health screening.
What it detects: An elevated WBC count (leukocytosis) often signals infection or inflammation, while a low count (leukopenia) can reflect bone marrow suppression, certain infections, or autoimmune disease, and raises infection risk.
Collection & prep: A standard blood draw from a vein in the arm, as part of a CBC. No special preparation is typically required.
Results:
High – often reflects infection, inflammation, or, less commonly, a blood cancer like leukemia
Low – raises infection risk; can reflect bone marrow suppression or certain viral infections
Normal – typically 4,500–10,000 cells/mcL
Possible complications of abnormal WBC: An abnormal total count is usually followed by a differential to see which specific white cell type is driving the change, since that distinction points toward very different causes and next steps.
Statements made in the Clinical Manual have not been evaluated by the FDA. The products mentioned are not intended to diagnose, treat, cure or prevent any disease.
