what is a cortisol level
Overview. A cortisol level test uses a blood sample to measure the level of cortisol present in blood. Cortisol is a steroid hormone released by the adrenal gland. The adrenal glands sit atop the kidneys.here are certain diseases, such as Addisonâs disease and Cushingâs disease, which affect the amount of cortisol produced by the adrenal gland. The test is used in the diagnosis of these diseases and as a way to assess the functioning of the adrenal and pituitary glands.