What is the normal range for white blood cell count and what does it indicate?

The normal white blood cell count is 4,500 to 11,000 cells per microliter. Leukocytosis, above 11,000, most commonly indicates bacterial infection, inflammation, stress, or corticosteroid use. Leukopenia, below 4,500, indicates bone marrow suppression from chemotherapy, radiation, or medications, immunodeficiency, or overwhelming infection. Neutropenia, specifically a neutrophil count below 1,500, places the patient at high risk for infection and requires protective isolation.