Synonyms: Cortisol, Random

Why It Is Done

*Problems of the pituitary gland or adrenal glands, such as producing too much or too little hormones.

Test Overview

A cortisol test is done to measure the level of the hormone cortisol in the blood, which may indicate problems with the adrenal glands or pituitary gland. Cortisol is produced by the adrenal glands. Cortisol levels increase when the pituitary gland releases another hormone called adrenocorticotropic hormone (ACTH).

Cortisol has many functions. It helps the body break down food for energy (metabolism), and it helps the body manage stress. Cortisol levels can be affected by many conditions, such as physical or emotional stress, strenuous activity, infection, or injury.

Normally, cortisol levels rise during the early morning hours and are highest in midmorning (about 7 a.m.). They drop very low in the evening and during the early phase of sleep. However, if you sleep during the day and are up at night, this pattern may be reversed. The absence of this daily variation (diurnal rhythm) in cortisol levels may be one of the first signs of overactive adrenal glands, especially Cushing's syndrome.

How To Prepare

You may be asked to avoid strenuous physical activity the day before a cortisol test. You may also be asked to lie down and relax for 30 minutes before the blood test is done.