Test Catalog

Test Id : IL6

Interleukin 6, Plasma

Useful For
Suggests clinical disorders or settings where the test may be helpful

Evaluation of patients with suspected systemic inflammation associated with infections, autoimmunity, and cancers

Method Name
A short description of the method used to perform the test

Electrochemiluminescence (ECL)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Interleukin 6, P

Lists additional common names for a test, as an aid in searching



Specimen Type
Describes the specimen type validated for testing

Plasma EDTA

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube: Lavender-top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Immediately after specimen collection, place the tube on wet ice.

2. Centrifuge at 1500 x g for 10 minutes and aliquot plasma into plastic vial.

3. Freeze specimen within 30 minutes.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.3 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Gross lipemia Reject
Gross icterus OK
Heat-treated specimen Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma EDTA Frozen (preferred) 21 days
Refrigerated 24 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Evaluation of patients with suspected systemic inflammation associated with infections, autoimmunity, and cancers

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Interleukin-6 (IL-6) is an important pro-inflammatory cytokine, which plays critical roles in both innate and adaptive immunity.(1,2) IL-6 is produced by a variety of different cell types, including macrophages, endothelial cells, and T cells. Its production can be initiated in response to microbial invasion or other cytokines, such as tumor necrosis factor alpha (TNF-alpha) and IL-1 beta. As part of the innate immune system, IL-6 acts on hepatocytes to induce expression of C-reactive protein, fibrinogen, and serum amyloid A, also known as the acute phase reactants. IL-6 also plays a key role in activating antibody-producing B cells to proliferate, leading to an enhanced antibody response.(1)


Under normal conditions, IL-6 plays an important role in cellular homeostasis. However, during inflammatory conditions, the concentration of IL-6 increases in several folds, highlighting its clinical relevance as a major alarm signal in humans in response to infections (sepsis/septicemia), inflammation, autoimmunity, and cancer.(2-4) Increased concentrations of IL-6 have been reported in localized (prosthetic joint infections [PJI], periodontitis), and systemic (eg, sepsis, COVID-19) infections, autoimmune conditions (eg, rheumatoid arthritis [RA] systemic lupus erythematosus, ankylosing spondylitis, and inflammatory bowel disease), and cancers.(4-8) Thus, IL-6 serum levels have evaluated and reported to predict severity and response to IL-6 targeted therapies in PJI,(4) sepsis,(5) COVID-19,(6) and RA.(7-8) Overall, IL-6 cytokine is a nonspecific biomarker of systemic inflammation that may have relevance in clinical decision making in the appropriate context.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =1.8 pg/mL

Provides information to assist in interpretation of the test results

Elevated concentrations of interleukin-6 (IL-6) may indicate an ongoing inflammatory response.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Interleukin-6 (IL-6) is a nonspecific marker associated with an inflammatory response and is not diagnostic for any specific disease or disease process. Elevated concentrations of IL-6 must be interpreted within the clinical context of the patient.


Normal concentrations of IL-6 do not exclude the possibility of an ongoing inflammatory process.


IL-6 has limited stability. Following centrifugation, plasma must be either immediately frozen or refrigerated. Specimens can be stored at refrigerated temperatures for only 24 hours, after which they must be frozen. Storage of plasma for any length of time at ambient temperature is not acceptable.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Hilligan KL, Ronchese F: Antigen presentation by dendritic cells and their instruction of CD4+ T helper cell responses. Cell Mol Immunol. 2020 Jun;17(6):587-599

2. Rose-John S: Interleukin-6 signalling in health and disease. F1000Res. 2020 Aug 20;9:F1000 Faculty Rev-1013

3. Jones SA, Jenkins BJ: Recent insights into targeting the IL-6 cytokine family in inflammatory diseases and cancer. Nat Rev Immunol. 2018 Dec;18(12):773-789

4. Rose-John S, Winthrop K, Calabrese L: The role of IL-6 in host defence against infections: immunobiology and clinical implications. Nat Rev Rheumatol. 2017 Jul;13(7):399-409

5. Gallo J, Svoboda M, Zapletalova J, et al: Serum IL-6 in combination with synovial IL-6/CRP shows excellent diagnostic power to detect hip and knee prosthetic joint infection. PLoS One. 2018 Jun;13(6):e0199226

6. Song J, Park DW, Moon S, et al: Diagnostic and prognostic value of interleukin-6, pentraxin 3, and procalcitonin levels among sepsis and septic shock patients: a prospective controlled study according to the Sepsis-3 definitions. BMC Infect Dis. 2019 Nov;19(1):968

7. Galvan-Roman JM, Rodriguez-Garcia SC, Roy-Vallejo E, et al: IL-6 serum levels predict severity and response to tocilizumab in COVID-19: an observational study. J Allergy Clin Immunol. 2021 Jan;147(1):72-80

8. Udomsinprasert W, Jittikoon J, Sangroongruangsri S, Chaikledkaew U: Circulating levels of interleukin-6 and interleukin-10, but not tumor necrosis factor-alpha, as potential biomarkers of severity and mortality for COVID-19: Systematic review with meta-analysis. J Clin Immunol. 2021 Jan;41(1):11-22

9. Boyapati A, Schwartzman S, Msihid J, et al: Association of high serum interleukin-6 levels with severe progression of rheumatoid arthritis and increased treatment response differentiating sarilumab from adalimumab or methotrexate in a post hoc analysis. Arthritis Rheumatol. 2020 Sept;72(9):1456-1466

Method Description
Describes how the test is performed and provides a method-specific reference

The interleukin-6 (IL-6) cytokine assay measures human cytokines in a 96-well spotted plate. The assay employs a sandwich immunoassay format where capture antibodies are coated on a single spot on the bottom of each well. Diluted samples, calibrators, and controls are added to the plate. If present, IL-6 will bind to the capture antibodies. After incubation, a solution containing detection antibodies conjugated with electrochemiluminescent labels is added. After a final incubation, a buffer is added that creates the appropriate chemical environment for electrochemiluminescence. The plate is then read on the MSD QuickPlex SQ120. The machine applies a voltage that causes bound labels to emit measurable light. The MSD QuickPlex SQ120 measures the intensity of emitted light and correlates it to a set of standards of known quantity via a 4-point logistics curve fitting method.(Package insert: Human IL-6 V-plex. Mesoscale Discovery; 2014)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Wednesday, Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 8 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
IL6 Interleukin 6, P 26881-3
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
63020 Interleukin 6, P 26881-3

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports