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.
Cortisol can also be measured using a urine or saliva test.
Your doctor will likely have you do the test early in the morning. This is important because cortisol level varies throughout the day.
You may be asked not to do any vigorous exercising the day before the test.
You may also be told to temporarily stop taking medicines that can affect the test, including:
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
The test is done to check for increased or decreased cortisol production. Cortisol is a glucocorticoid (steroid) hormone released from the adrenal gland in response to adrenocorticotropic hormone (ACTH). ACTH is a hormone released from the pituitary gland in the brain.
Cortisol affects many different body systems. It plays a role in:
Different diseases, such as Cushing syndrome and Addison disease, can lead to either too much or too little production of cortisol. Measuring blood cortisol level can help diagnose these conditions. It is also measured to evaluate how well the pituitary and adrenal glands are working.
The test is often done before and 1 hour after injection of a medicine called ACTH (cosyntropin). This part of the test is called an ACTH stimulation test. It is an important test that helps check the function of the pituitary and adrenal glands.
The test is often done in the morning after taking 1 milligram (mg) of dexamethasone the night before the test.
Other conditions for which the test may be ordered include:
Normal values for a blood sample taken at 8 in the morning are 5 to 25 mcg/dL or 140 to 690 nmol/L.
Normal values depend on the time of day and the clinical context. Normal ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.
The expected result can be outside the normal range if done as part of a cosyntropin stimulation test or dexamethasone suppression test.
A higher than normal level may indicate:
A lower than normal level may indicate:
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
Chernecky CC, Berger BJ. Cortisol - plasma or serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:388-389.
Newell-Price JDC, Auchus RJ. The adrenal cortex. In: Melmed S, Auchus, RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 15.BACK TO TOP
Review Date: 5/13/2021
Reviewed By: Brent Wisse, MD, Board Certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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