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Interleukin-6 (IL-6) Serum/plasma Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of interleukin-6, a protein involved in inflammation and immune response, in your blood.

Quick summary

["IL-6 helps your body respond to infections, injuries, and chronic conditions by signaling inflammation."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
4650-8
Short code
Il1 SerPl-aCnc
Synonyms
Il1 SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Interleukin-6 Used For?

IL-6 levels may be checked to diagnose or monitor conditions like infections, autoimmune diseases (such as rheumatoid arthritis), inflammatory disorders, or certain cancers. It can also help assess how your body is responding to treatments for these conditions.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab for testing using an immunoassay method to measure IL-6 concentration.

What Might Affect IL-6 Levels?

Several factors can influence IL-6 levels, including recent infections, injuries, stress, certain medications, or underlying health conditions like heart disease or cancer. Smoking, obesity, or chronic inflammation may also play a role.

When Might You Need This Test?

Your doctor may order an IL-6 test if you have symptoms of inflammation, suspected autoimmune disease, or if you’re undergoing treatment for a condition that affects inflammation, such as chemotherapy or biologics for arthritis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IL-6’s Role in Health and Disease

Short name

IL-6

Frequently asked questions

Why might my doctor want to check my IL-6 levels?
IL-6 is a key marker for inflammation and immune activity. Elevated levels can signal infections, autoimmune diseases (like lupus or rheumatoid arthritis), or other inflammatory conditions. Your doctor may use it to guide treatment decisions or track disease progression.
What are the normal ranges for IL-6?
IL-6 reference ranges vary by lab and individual factors like age and health status. Your results will be compared to ranges specific to your lab and medical context, not a single universal range.
How soon will I get my results?
Results typically take 1–3 business days, depending on lab processing times. Your doctor will discuss them with you during your follow-up visit.
  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 16, 2026. · Read our editorial policy