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Neutrophil-to-Lymphocyte Ratio (NLR) in Plasma/Serum

Published: August 9, 2026Updated: August 17, 2026

This test measures the ratio of neutrophils to lymphocytes in your blood, a simple way to assess immune response and inflammation.

Quick summary

["NLR helps doctors check how your body’s immune system is reacting to infection or illness."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
77622-9
Short code
NT-proBNP DiafP IA-mCnc
Synonyms
NT-proBNP DiafP IA-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
100
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
83880
SNOMED
394971007
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is Neutrophil-to-Lymphocyte Ratio (NLR)?

Neutrophils are a type of white blood cell that fight off infections, while lymphocytes help regulate the immune system. The NLR compares their numbers. A higher ratio may suggest inflammation or infection, while a lower ratio might indicate immune suppression or other conditions.

Why Might You Need This Test?

Your doctor may order this test to evaluate symptoms like fever, fatigue, or unexplained weight loss, or to monitor conditions like cancer, infections, or autoimmune diseases.

How Is the Test Done?

A small blood sample is taken from a vein, usually in your arm. The blood is processed to separate and count neutrophils and lymphocytes, then the ratio is calculated.

What Does the Test Result Mean?

Results are not given as a single number but as a ratio (e.g., 2.5:1). Higher ratios may indicate acute inflammation or infection, while lower ratios could suggest chronic conditions or immune dysfunction. Your doctor will interpret results in the context of your overall health.

Reference range

Normal: <100 pg/mLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

NLR (Plasma/Serum)

Frequently asked questions

What causes a high NLR?
A high NLR can occur with infections (like pneumonia or urinary tract infections), inflammatory diseases (such as rheumatoid arthritis), or certain cancers. It may also appear after surgery or trauma.
What causes a low NLR?
A low NLR might be seen in chronic infections, certain cancers (like lymphoma), or conditions that suppress the immune system, such as HIV or chemotherapy treatment.
Can lifestyle or diet affect NLR?
While diet and lifestyle factors like stress or exercise may influence immune cell activity indirectly, NLR is primarily a blood test result and not directly affected by diet alone. Your doctor may recommend lifestyle changes if they suspect underlying conditions affecting your immune response.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy