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  • Also Known As:
  • IL-6
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At a Glance

Why Get Tested?

To help monitor inflammatory responses such as infection, sepsis, lupus, or rheumatoid arthritis or to evaluate diabetes, stroke, and cardiovascular disease

When To Get Tested?

Not commonly ordered, but may be used when an individual has been diagnosed with or has signs and symptoms associated with one of the conditions listed above

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Interleukin-6 (IL-6) is a protein produced by various cells. It helps regulate immune responses, which makes the IL-6 test potentially useful as a marker of immune system activation. IL-6 can be elevated with inflammation, infection, autoimmune disorders, cardiovascular diseases, and some cancers. The test measures the amount of IL-6 in the blood.

Interleukin-6 is one of a large group of molecules called cytokines. Cytokines have multiple roles to play within the body and act especially within the immune system to help direct the body’s immune response. They are a part of the “inflammatory cascade” that involves the coordinated, sequential activation of immune response pathways.

IL-6 acts on a variety of cells and tissues. It promotes differentiation of B-cells (white blood cells that produce antibodies), promotes cell growth in some cells, and inhibits growth in others. It stimulates the production of acute phase proteins. IL-6 also plays a role in body temperature regulation, bone maintenance, and brain function. It is primarily pro-inflammatory but can also have anti-inflammatory effects.

Common Questions

How is the test used?

Interleukin-6 (IL-6) may be used to help evaluate a person who has a condition associated with inflammation, such as lupus or rheumatoid arthritis, or with infection, such as sepsis. It may also be used in the evaluation of diabetes, stroke, or cardiovascular disease.

When is it ordered?

The IL-6 test is not frequently ordered. C-reactive protein (CRP) is the most commonly ordered test to evaluate inflammation, but IL-6 may be ordered in conjunction with or following a CRP test when a person has signs and symptoms of an inflammatory condition or infection and a health care practitioner wants additional information.

What does the test result mean?

Normally, IL-6 is not detected in the blood or is present in low levels.

An elevated IL-6 may mean that the person tested has an inflammatory condition. IL-6 is elevated with a variety of conditions and has been associated in some cases with an increased risk of disease development or worsening prognosis. An increase in IL-6 may be seen in conditions such as:

  • Rheumatoid arthritis, lupus, and other autoimmune disorders
  • Infections
  • Sepsis
  • Some cancers
  • Diabetes
  • Cardiovascular disease
  • Stroke

Is there anything else I should know?

Tocilizumab, a drug that targets the IL-6 receptor and blocks the action of IL-6, is being prescribed to some patients with rheumatoid arthritis. This drug reduces inflammation and slows the progression of joint destruction. Additional drugs that target IL-6 (or other cytokines) are being researched and developed.

The usefulness of the IL-6 test in the medical setting is still being established. Medical researchers are actively studying IL-6 and other cytokines to better understand the normal functions of these proteins within the immune system and their association with a variety of diseases and conditions. The goal is to determine whether IL-6 is causing or contributing to disease states. This will show how it may be used to help in the diagnosis, treatment, and monitoring of diseases. It may be used to help guide treatment or even as a target for the treatment of these conditions.

Can IL-6 be measured in samples other than blood?

Interleukin-6 may sometimes be measured in other body fluids, such as joint fluid (synovial fluid) and cerebrospinal fluid.

How long will it take for my results?

This is not a routine test and not all laboratories offer this test. It is most likely that your sample will be sent to a reference laboratory for testing and it may take from one to several days for results to be available.

Can I lower my IL-6 level?

Concentrations of IL-6 will decrease with a decrease in inflammation but there is not currently evidence that IL-6 levels respond to lifestyle changes.

View Sources

Sources Used in Current Review

2019 review performed by Sarah E Wheeler PhD, FAACC, Assistant Professor University of Pittsburgh, Medical Director Automated Testing Laboratories UPMC Mercy, UPMC Children’s Hospital, Associate Medical Director Clinical Immunopathology UPMC Presbyterian, Shadyside, Magee Women’s Hospital.

Dieplinger B, Bocksrucker C, Egger M, Eggers C, Haltmayer M, Mueller T. Prognostic Value of Inflammatory and Cardiovascular Biomarkers for Prediction of 90-Day All-Cause Mortality after Acute Ischemic Stroke-Results from the Linz Stroke Unit Study. Clin Chem. 2017 Jun;63(6):1101-1109.

Akbari M, Hassan-Zadeh V. IL-6 signalling pathways and the development of type 2 diabetes. Inflammopharmacology. 2018 Jun;26(3):685-698.

Fan SL, Miller NS, Lee J, Remick DG. Diagnosing sepsis – The role of laboratory medicine. Clin Chim Acta. 2016 Sep 1;460:203-10.

Unver N, McAllister F. IL-6 family cytokines: Key inflammatory mediators as biomarkers and potential therapeutic targets. Cytokine Growth Factor Rev. 2018 Jun;41:10-17.

Vainer N, Dehlendorff C, Johansen JS. Systematic literature review of IL-6 as a biomarker or treatment target in patients with gastric, bile duct, pancreatic and colorectal cancer. Oncotarget. 2018 Jul 3;9(51):29820-29841.

Scheller J, Chalaris A, Schmidt-Arras D, Rose-John S. The pro- and anti-inflammatory properties of the cytokine interleukin-6. Biochim Biophys Acta. 2011 May;1813(5):878-88.

Kamimura D, Ishihara K, Hirano T. IL-6 signal transduction and its physiological roles: the signal orchestration model. Rev Physiol Biochem Pharmacol. 2003;149:1-38.

Ibrahim NE, Januzzi JL Jr. Beyond Natriuretic Peptides for Diagnosis and Management of Heart Failure. Clin Chem. 2017 Jan;63(1):211-222.

Duprez DA, Otvos J, Sanchez OA, Mackey RH, Tracy R, Jacobs DR Jr. Comparison of the Predictive Value of GlycA and Other Biomarkers of Inflammation for Total Death, Incident Cardiovascular Events, Noncardiovascular and Noncancer Inflammatory-Related Events, and Total Cancer Events. Clin Chem. 2016 Jul;62(7):1020-31.

Sources Used in Previous Reviews

Lowe, G. et. al. (2014). Circulating Inflammatory Markers and the Risk of Vascular Complications and Mortality in People With Type 2 Diabetes and Cardiovascular Disease or Risk Factors: The ADVANCE Study Medscape Multispecialty from Diabetes. 2014;63(3):1115-1123. [On-line information]. Available online at http://www.medscape.com/viewarticle/821358. Accessed June 2014.

Genzen, J. (Updated 2014 May). Acute Phase Proteins – Acute Phase Reactants. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/AcutePhaseReactants.html?client_ID=LTD#tabs=0. Accessed June 2014.

Erta, M. et. al. (2012 October 25). Interleukin-6, a Major Cytokine in the Central Nervous System. Int J Biol Sci. 2012; 8(9): 1254–1266. [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491449/. Accessed June 2014.

Ferrari, R. et. al. (2013). Three-Year Follow-Up of Interleukin 6 and C-Reactive Protein in Chronic Obstructive Pulmonary Disease. Medscape Multispecialty from Respiratory Research. 2013;14(24) [On-line information]. Available online at http://www.medscape.com/viewarticle/804945. Accessed June 2014.

Check, W. (2011 March). Viewing inflammation, with markers new and old. CAP Today [On-line information]. Available online through http://www.cap.org. Accessed June 2014.

Kaptoge, S. et. al. (2014). Inflammatory Cytokines and Risk of Coronary Heart Disease New Prospective Study and Updated Meta-analysis. Medscape Multispecialty from Eur Heart J. 2014;35(9):578-589. [On-line information]. Available online at http://www.medscape.com/viewarticle/821753. Accessed June 2014.

Barnes, T. et. al. (2011 July). The Many Faces of Interleukin-6: The Role of IL-6 in Inflammation, Vasculopathy, and Fibrosis in Systemic Sclerosis. International Journal of Rheumatology Volume 2011, Article ID 721608 [On-line information]. Available online at http://www.hindawi.com/journals/ijr/2011/721608/. Accessed June 2014.

Scheller, J. and Rose-John, S. (2012 July 28). The interleukin 6 pathway and atherosclerosis. The Lancet, Volume 380, Issue 9839, p 338. [On-line information]. Available online at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)61246-X/fulltext. Accessed June 2014.

Kristiansen, O. and Mandrup-Poulsen, T. (2005 December). Interleukin-6 and Diabetes, The Good, the Bad, or the Indifferent? Diabetes, V 54 (2) [On-line information]. Available online at http://diabetes.diabetesjournals.org/content/54/suppl_2/S114.full. Accessed June 2014.

Lehman, C. and Meikle, A. W. (Updated 2013 September). Ischemic Heart Disease – IHD. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/IHD.html?client_ID=LTD#tabs=0. Accessed June 2014.

O’Reilly, S. et. al. (2013 April 12). Interleukin-6: a new therapeutic target in systemic sclerosis? Clinical & Translational Immunology (2013) 2, e4; doi:10.1038/cti.2013.2 [On-line information]. Available online at http://www.nature.com/cti/journal/v2/n4/full/cti20132a.html. Accessed June 2014.

Schellera, J. et. al. (2011 May). The pro- and anti-inflammatory properties of the cytokine interleukin-6. Biochimica et Biophysica Acta 1813 (2011) 878–888 [On-line information]. Available online at http://www.sciencedirect.com/science/article/pii/S0167488911000425. Accessed June 2014.

Lewis, R. (2013 September 16). Chronic Inflammation May Preclude Healthy Aging. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/811107. Accessed June 2014.

Nainggolan, L. (2012 March 15). Gene Studies: IL-6 Pathway Has Causal Role in Heart Disease. Medscape Multispecialty [On-line information]. Available online at http://www.medscape.com/viewarticle/760285. Accessed June 2014.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 348-349.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 489.


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