The cortisol blood test measures the level of cortisol in the blood. Cortisol is a steroid (glucocorticoid or corticosteroid) hormone produced by the adrenal gland. A cortisol test is used to help diagnose disorders of the adrenal gland. These include Cushing's syndrome, a condition that causes your body to make too much cortisol, and Addison disease, a condition in which your body doesn't make enough cortisol.
