Biomarker · Blood cells

White blood cell count

Also known as: WBC, WCC, leucocyte count, white cell count

The total number of white blood cells in a volume of blood: the immune cells that fight infection and drive inflammation. The differential then splits the total into neutrophils, lymphocytes, monocytes, eosinophils and basophils.

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Also known as
WBC, WCC, leucocyte count, white cell count
Units
×10⁹/L (cells per litre); the same number as thousands per microlitre in US units
Measured by
Full blood count, CRP test

What it is and what it does

White cells are made in the bone marrow and travel through blood to the tissues where they work. The count rises quickly when the marrow releases stored neutrophils in response to bacterial infection, tissue injury, steroids or stress, and falls when the marrow is suppressed, when cells are consumed faster than they are made, or in some viral infections. The total count on its own is only a starting point: the differential says which cell line has changed, and a blood film shows what the cells look like.

Why it may be higher

  • Bacterial infection and sepsis (mostly neutrophils)
  • Inflammation, tissue damage, burns, heart attack
  • Corticosteroid treatment, smoking, stress and heavy exercise
  • Leukaemia and other bone-marrow disorders
  • After the spleen is removed

Why it may be lower

  • Viral infections, including influenza and HIV
  • Chemotherapy, radiotherapy and some medicines (for example clozapine, carbimazole, methotrexate)
  • Bone-marrow failure or infiltration
  • Severe sepsis (consumption), some autoimmune diseases, B12 or folate deficiency
  • A normal variant in some people of African or Middle Eastern ancestry (benign ethnic neutropenia)

A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.

What can affect the result

  • Time of day, exercise, smoking and pregnancy
  • Recent steroid or adrenaline-type medicines
  • Sample clumping or delays can give a spurious count
Reference ranges. Reference intervals for this marker depend on the laboratory, the assay, the units, age, sex and pregnancy. Interpret a result against the interval printed on the laboratory report, not against a figure from the internet.

Medicines that can change it

Amoxicillin

Each medicine page lists its effect on this marker under "Effects on tests and results", with the source.

Educational content. A biomarker page explains what a substance is and why its level can change. It cannot determine the cause of your result: interpret a result using the range supplied by the laboratory that performed the test, with the clinician who ordered it.