What Is WBC (White Blood Cell Count) in a Blood Test?

Q: What Is WBC (White Blood Cell Count) in a Blood Test?

WBC explained: normal range 4,500-11,000/µL, what high WBC (infection, inflammation) and low WBC (bone marrow suppression, viral infection) mean, plus the 5 types of white blood cells.

WBC stands for White Blood Cell Count. White blood cells are your immune system's defense against infection and inflammation.

Normal Range

4,500–11,000 cells/µL for adults

The Five Types

Neutrophils (40–60%) — bacterial defense
Lymphocytes (20–40%) — viral defense, antibodies
Monocytes (2–8%) — become macrophages
Eosinophils (1–4%) — parasites, allergies
Basophils (0.5–1%) — histamine release

High WBC Causes

Bacterial infection — most common cause
Inflammation — autoimmune disease
Physical stress — exercise, surgery
Leukemia — markedly elevated
Corticosteroid use
Smoking

Low WBC Causes

Viral infection
Bone marrow suppression — chemotherapy
Autoimmune disease — lupus
Certain medications
HIV/AIDS
Severe malnutrition

Source: NLM MedlinePlus, American Association for Clinical Chemistry.

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