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A cortisol test is done to measure the level of the hormone cortisol in the blood. The cortisol level may show problems with the adrenal glands or pituitary gland. Cortisol is made by the adrenal glands. Cortisol levels go up when the pituitary gland releases another hormone called adrenocorticotropic hormone (ACTH).
Cortisol has many functions. It helps the body use sugar (glucose) and fat 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 about 7 a.m. They drop very low in the evening and during the early phase of sleep. But if you sleep during the day and are up at night, this pattern may be reversed. If you do not have this daily change (diurnal rhythm) in cortisol levels, you may have overactive adrenal glands. This condition is called Cushing's syndrome.
The timing of the cortisol test is very important because of the way cortisol levels vary throughout a day. If your doctor thinks you might make too much cortisol, the test will probably be done late in the day. If your doctor thinks you may not be making enough, a test is usually done in the morning.
A cortisol test is done to find problems of the pituitary gland or adrenal glands, such as making too much or too little hormones.
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.
Many medicines may change the results of this test. Some medicines, such as steroids, can affect cortisol levels for some time even after you stop taking the medicine. Be sure to tell your doctor about all the non-prescription and prescription medicines you take.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
The health professional drawing your blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
A cortisol test is done to measure the level of the hormone cortisol in the blood.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
5–23 micrograms per decilitre (mcg/dL) or 138–635 nanomoles per litre (nmol/L)
3–16 mcg/dL or 83–441 nmol/L
2–11 mcg/dL or 55–304 nmol/L
Reasons you may not be able to have the test or why the results may not be helpful include:
To learn more, see:
CitationsFischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Other Works ConsultedChernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Current as ofNovember 6, 2018
Author: Healthwise StaffMedical Review: E. Gregory Thompson, MD - Internal MedicineDonald Sproule, MDCM, CCFP - Family MedicineAdam Husney, MD - Family MedicineKathleen Romito, MD - Family MedicineAlan C. Dalkin, MD -
Current as of: November 6, 2018
Author: Healthwise Staff
Medical Review:E. Gregory Thompson, MD - Internal Medicine & Donald Sproule, MDCM, CCFP - Family Medicine & Adam Husney, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & Alan C. Dalkin, MD -
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