Interleukin-6, Serum

Interleukin-6 (IL-6) is a signaling protein your immune system produces during inflammation and stress. It is measured to assess your body's inflammatory state and can indicate how well your immune system is responding to infection, injury, or chronic conditions.

When elevated: Elevated IL-6 typically signals active inflammation in your body, which may occur with infection, autoimmune disease, chronic inflammatory conditions, or significant physical stress. Persistently high levels are also associated with increased cardiovascular risk and poor metabolic health. When low: Low IL-6 levels are generally favorable and indicate minimal systemic inflammation. Extremely low levels are uncommon and not typically clinically concerning unless part of a broader immune dysfunction pattern.

IL-6 rises acutely during and immediately after intense exercise as a signaling molecule that supports muscle adaptation and recovery—it's not inherently harmful in this context. Chronically elevated resting IL-6, however, may reflect inadequate recovery, overtraining syndrome, or systemic inflammation that can slow adaptation and increase injury risk. Tracking trends over time is more useful than single values for athletes optimizing training balance.