IL-6 (Interleukin-6)

Interleukin-6 (IL-6) is a versatile cytokine. It is made by immune cells, fat cells, blood-vessel cells, and senescent cells. It signals two ways: through a membrane-bound receptor (classical signaling) or a soluble one (trans-signaling), with different effects in different tissues. In short bursts, IL-6 is useful. It drives your liver's acute-phase response (raising CRP, fibrinogen, and serum amyloid A) and is essential for fighting infection. After hard exercise, your muscles release a lot of it briefly, acting as a 'myokine'. The problem is chronic elevation. Steady high IL-6, as in chronic inflammation, obesity, and aging (inflammaging), independently predicts death from all causes and from heart disease across many large studies. That prediction holds even after accounting for CRP. In longevity research, IL-6 is a central marker of inflammaging and a drug target under study, since high IL-6 feeds pathways tied to muscle loss, cognitive decline, frailty, and cancer.

Last reviewed: June 22, 2026

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