The Cortisol Free Serum Test is a laboratory test used to measure the level of free (unbound) cortisol in the blood. Cortisol is a hormone produced by the adrenal glands that plays a key role in stress response, metabolism, immune function, and blood pressure regulation.

This test helps healthcare providers evaluate adrenal gland function and assess conditions related to abnormal cortisol levels, such as chronic stress, adrenal disorders, or hormonal imbalances. Measuring free cortisol provides insight into the biologically active portion of cortisol available to the body.