Neutrophil-to-Lymphocyte Ratio (NLR)
Simple inflammatory index calculated from FBC. Elevated NLR (>3.5–5) indicates systemic inflammation, infection, or stress. Useful prognostic marker in sepsis, cancer, cardiovascular disease, and COVID-19. Low NLR (<1) may suggest immunosuppression or viral illness.
Score interpretation
NLR <1 — lower than normal; consider viral infection, immunosuppression, or haematological cause
→ Review clinical context; check for lymphocytosis (viral illness — EBV, CMV, pertussis); consider bone marrow pathology if isolated; review immunosuppressive medications; not typically alarming in isolation but correlate with clinical picture
NLR 1.0–3.5 — normal range; no significant inflammatory response
→ Normal inflammatory profile; continue clinical assessment; if patient symptomatic, correlate with CRP, ESR, and clinical picture; NLR alone not diagnostic; repeat if condition changes
NLR 3.5–5.0 — mildly elevated; reflects inflammatory or physiological stress response
→ Consider infection, inflammatory condition, tissue injury, or physiological stress (surgery, MI, trauma); correlate with CRP, PCT, cultures; clinical assessment; monitor trend; not independently diagnostic; serial measurement more useful than single value
NLR 5.1–10 — elevated; significant inflammatory or immune response
→ Active infection or inflammatory condition likely; consider sepsis (assess NEWS2/qSOFA); malignancy (NLR correlates with poorer prognosis in many cancers); review clinical context; blood cultures if sepsis suspected; escalate care if haemodynamically compromised; NLR >5 associated with worse outcomes in COVID-19, MI, sepsis
NLR >10 — markedly elevated; associated with severe illness
→ Severe systemic stress, sepsis, or advanced malignancy; assess for septic shock (qSOFA, NEWS2); haematology review if lymphopaenia unexplained; escalate care; ITU consideration if haemodynamically unstable; address underlying cause; NLR >10 in COVID-19 associated with ICU admission risk; document and trend
Interpretation bands for the NLR Calculator. Apply clinical judgement and local guidance.
References
- Forget P et al. What is the normal value of the neutrophil-to-lymphocyte ratio? BMC Res Notes. 2017;10(1):12.
Related
Curated clinical cross-links plus same-class fallbacks.
- Colchicine (Pericarditis / Post-MI Inflammation) · Pericarditis / Coronary Inflammation
- Dapsone · Anti-inflammatory / Antimicrobial
- Colchicine · Anti-inflammatory — Neutrophilic Dermatoses / Vasculitis
- Belimumab (Cutaneous Lupus) · BLyS/BAFF Inhibitor (Anti-B-Lymphocyte Stimulator)
- Dexamethasone · Corticosteroid — ENT Inflammation / Croup
- Diclofenac · Non-Steroidal Anti-Inflammatory Drug (NSAID)
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.