# Neutrophil-to-lymphocyte ratio (NLR)

Neutrophils divided by lymphocytes, the simplest reading of the balance between the immune system's first responders and its regulators, from a blood count you already have.

Type: index · Unit: ratio · Domain: Cardio-Respiratory Health · Accuracy: Calculated · Importance: Supporting

Also called: neutrophil lymphocyte ratio, white cell ratio, inflammation ratio

## In one sentence

Neutrophils divided by lymphocytes, the simplest reading of the balance between the immune system's first responders and its regulators, from a blood count you already have.

## Why it matters

It is the cheapest inflammation ratio in medicine and the simpler cousin of the Systemic Immune-Inflammation Index, and its reference range in healthy people was measured directly: in 413 working adults aged 21 to 66 attending a health-prevention program, the mean ratio was 1.65 and the 95 percent limits ran from 0.78 to 3.53, confirmed in a second healthy group on different analyzers (Forget 2017). Values above about 3 are where the clinical literature starts to read the balance as tilted, which the clinician specification states as the reference point; the cohort findings for the index above apply to the ratio in the same direction and at the same strength.

## What moves it

An infection or injury (up within hours), hard exercise (up for hours), acute psychological stress (lymphocytes fall), smoking, corticosteroids, time of day, and age. It settles within a week or two of whatever moved it.

## How to measure it well

From a blood count taken under the panel's rules; the morning, rested, well for two weeks, no hard training for 48 hours. Compare draws taken the same way.

## How Vitality Tracker uses it

Computed from one draw only and shown on the labs dashboard beside the counts and the index, with the healthy-adult limits from the Belgian study shown as that study's and the clinical reference point of about 3 as the specification's, never as VT's verdict. No working optimal line is drawn; a draw taken while unwell is excluded.

## How far to trust the number

Calculated from two precise counts; the variation is biological and large, so one ratio outside the healthy limits is a reason to repeat the count when well, not a finding.

## Method

NLR = neutrophils (×10⁹/L) ÷ lymphocytes (×10⁹/L), from the absolute counts, not the percentages.

## Sources

1. Forget P, Khalifa C, Defour JP, Latinne D, Van Pel MC, De Kock M. What is the normal value of the neutrophil-to-lymphocyte ratio? BMC Res Notes 2017;10:12. [doi:10.1186/s13104-016-2335-5](https://doi.org/10.1186/s13104-016-2335-5)
2. Xia Y, et al. J Clin Med 2023. [doi:10.3390/jcm12031128](https://doi.org/10.3390/jcm12031128)
3. Vitality Tracker, Clinician report content specification (derived indices).

## Related

- [Full blood count with differential](https://vitalitytracker.app/knowledge/full-blood-count)
- [Systemic Immune-Inflammation Index](https://vitalitytracker.app/knowledge/systemic-immune-inflammation-index)
- [CRP, high-sensitivity](https://vitalitytracker.app/knowledge/c-reactive-protein)
- [Getting your blood tests done in New Zealand](https://vitalitytracker.app/knowledge/blood-tests-in-new-zealand)

Reviewed October 2026 · v1

Source: https://vitalitytracker.app/knowledge/neutrophil-to-lymphocyte-ratio