Neutrophil-to-Lymphocyte Ratio – a simple inflammation marker.
NLR = Neutrophil count / Lymphocyte count. Normal NLR is 1–3. Elevated NLR is associated with worse outcomes in cardiovascular disease, cancer, infections, and COVID-19. NLR > 3 suggests systemic inflammation. It is an inexpensive, readily available marker from routine CBC that adds prognostic value across many conditions.