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IL6

Inflammation Biomarker

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Collection Type: Blood

Body System

Related System: Inflammation

Overview

Interleukin‑6 (IL‑6) is a pro‑inflammatory cytokine produced by immune cells (macrophages, T cells), endothelial cells and adipocytes. The IL‑6 blood test measures circulating IL‑6 concentration, typically by immunoassay, and reflects activation of the acute‑phase inflammatory response. Elevated IL‑6 is seen with infections (including sepsis), autoimmune and inflammatory disorders (e.g., rheumatoid arthritis), severe viral illness or cytokine release syndromes, and some malignancies. Symptoms prompting testing include fever, rapid clinical deterioration, unexplained systemic inflammation, severe respiratory distress, or suspected cytokine storm. Levels vary by assay and population: they tend to be higher in older adults, during pregnancy, in obesity, and with smoking; reference ranges differ in neonates and infants.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Inflammation - Symptoms indicating test: persistent fever, sudden clinical worsening, severe respiratory symptoms, unexplained systemic inflammation or organ dysfunction - Conditions diagnosed/monitored: sepsis, severe viral infections, autoimmune flares, cytokine release syndrome, certain cancers, monitoring response to anti‑inflammatory/biologic therapy - Reasons for abnormal levels: acute infection, chronic inflammation, immune activation, malignancy, tissue injury, obesity - Biological meaning of abnormal values: elevated IL‑6 signals active cytokine‑mediated inflammation and drives acute‑phase reactants (e.g., CRP) - Behaviors/lifestyle causing abnormal values: smoking, obesity, recent intense exercise, poor sleep, heavy alcohol use - Family history: strong family history of autoimmune or autoinflammatory disease may prompt testing

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Understanding Test Results

Values ≤7 pg/mL are generally considered within the expected range for most adults by common assays.
Mild elevations (≈8–20 pg/mL) suggest low‑grade inflammation, chronic inflammatory disease activity, or early/controlled infection.
Moderate elevations (≈20–100 pg/mL) indicate significant systemic inflammation or active infection, and warrant clinical correlation for conditions such as active autoimmune flare, bacterial infection or worsening respiratory illness.
High levels (>100 pg/mL) are associated with severe systemic inflammatory states: sepsis, cytokine release syndrome, macrophage activation syndrome, or severe viral illnesses and carry higher risk of organ dysfunction.
Very low or undetectable IL‑6 is typically not clinically concerning.
Interpret results with clinical context and note that reference limits and cutoffs vary by laboratory assay, age and pregnancy status.

Normal Range

0-7 pg/mL

FAQs

Q: What is the function of IL-6?

A: Interleukin‑6 (IL‑6) is a multifunctional cytokine that coordinates immune responses, inflammation and metabolism. It triggers the acute‑phase response in the liver (raising CRP), induces fever, promotes B‑cell differentiation into antibody‑secreting plasma cells, influences T‑cell differentiation (including Th17), supports hematopoiesis, and affects metabolism and bone turnover. IL‑6 can act as both a pro‑inflammatory and anti‑inflammatory mediator depending on context.

Q: Is IL-6 proinflammatory or anti-inflammatory?

A: Interleukin‑6 (IL‑6) is pleiotropic: it can be both proinflammatory and anti‑inflammatory depending on context. IL‑6 drives acute‑phase responses, fever, B‑cell and T‑cell activation and, via trans‑signaling, promotes inflammation. Conversely, IL‑6 induces anti‑inflammatory mediators (IL‑1 receptor antagonist, IL‑10) and supports tissue repair through classical signaling; chronic excess tends to be pathogenic.

Q: What is IL-6 a marker for?

A: Interleukin‑6 (IL‑6) is a pro‑inflammatory cytokine used as a biomarker of systemic inflammation and immune activation. Elevated IL‑6 indicates acute infection, sepsis, cytokine‑release syndromes, and active autoimmune diseases (e.g., rheumatoid arthritis), and correlates with severity in conditions like COVID‑19 and some cancers. Clinicians use IL‑6 levels to assess disease activity, prognosis, and response to therapy.

Q: Is IL-6 good or bad?

A: Interleukin‑6 (IL‑6) is neither simply good nor bad it’s context‑dependent. It helps coordinate immune responses, fight infections, and aid tissue repair, but when persistently or excessively elevated it drives chronic inflammation, autoimmunity, metabolic disturbances and can worsen severe infections through cytokine storms. Therapeutic strategies aim to balance its protective roles while limiting harmful long‑term or overactive IL‑6 signaling.

Q: What happens if interleukin-6 is high?

A: High interleukin‑6 (IL‑6) indicates systemic inflammation. It stimulates the acute‑phase response (fever, increased CRP), is elevated in infections, autoimmune or chronic inflammatory diseases, and can drive cytokine‑release syndromes causing tissue and organ damage. Persistent elevation is linked to worse outcomes and higher cardiovascular risk. High IL‑6 prompts further evaluation and treatment to control the underlying cause.

Q: What does IL-6 do to the brain?

A: Interleukin‑6 (IL‑6) is an immune signaling protein that acts in the brain to trigger acute neuroinflammation, induce fever and sickness behavior, and influence mood, cognition, synaptic plasticity and neurogenesis. Short‑term IL‑6 aids repair and host defense; chronically elevated IL‑6 increases blood–brain barrier permeability, sustains inflammation, and is linked to depression, cognitive decline and higher risk of neurodegenerative disorders.