The most abundant white cells; first responders to bacterial infection.
What it is
Neutrophils are granulocytes that engulf bacteria and debris. Absolute neutrophil count (ANC) in ×10⁹/L is preferred over percentage alone because percentages shift when other white cells change.
Why it matters
High neutrophils commonly accompany bacterial infection, inflammation, smoking, steroids, and acute physiological stress. Very low neutrophils raise infection risk; fever with severe neutropenia is an emergency.
Medicines, viral illness, autoimmune disease, and marrow disorders feature in the differential. Always read with symptoms and the rest of the white-cell differential.
This guide is educational only and cannot diagnose you. Discuss results, especially anything outside your laboratory’s reference interval, or that does not match how you feel, with a GP or other appropriately qualified clinician.
How it affects the body
Neutrophils exit blood into tissues quickly, releasing enzymes and reactive oxygen species that kill bacteria, and can collateral-damage tissue in intense inflammation. Marrow ramps production when demand is high.
For athletes
Post-race neutrophilia is common and usually short-lived. Persistent neutropenia in an athlete on a restricted diet or immunosuppressant needs medical input before foreign travel or crowded events.
