A cortisol test measures the level of the hormone cortisol in a 24-hour sample of urine. The cortisol level may show problems with the adrenal glands or the pituitary gland. Cortisol is made by the adrenal glands. Cortisol levels get higher when the pituitary gland releases adrenocorticotropic hormone (ACTH).
Cortisol has many functions. It helps the body use sugar (glucose) and fat for energy (metabolism). It helps the body manage stress. Cortisol levels can be affected by many things, 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 in cortisol levels, you may have overactive adrenal glands.
Cortisol levels vary widely throughout the day, so you collect urine over 24 hours for this test.
Why It Is Done
A cortisol test is done to find problems of the pituitary gland or adrenal glands, such as making too much hormone.
How To Prepare
You may be asked to avoid strenuous physical activity the day before the test.
Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription 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?).
How It Is Done
- You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated. This marks the beginning of your 24-hour collection period.
- For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
- Keep the large container in the refrigerator for the 24 hours.
- Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container, and record the time.
- Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.
How It Feels
This test does not cause any pain.
Collecting a 24-hour urine sample does not cause problems.
A cortisol test measures the level of the hormone cortisol in a 24-hour sample of urine.
These numbers are just a guide. The range for "normal" varies from lab to lab. Your lab may have a different range. Your lab report should show what range your lab uses for "normal." Also, your doctor will evaluate your results based on your health and other factors. So a number that is outside the normal range here may still be normal for you.
5-55 mcg or 14-152 nmol
2-27 mcg or 5-75 nmol
High values of cortisol may be caused by:
What Affects the Test
You may not be able to have the test, or the results may not be helpful, if:
- You feel physical or emotional stress.
- You are pregnant. This can cause urine cortisol levels to be high.
- You have low blood sugar (hypoglycemia).
- You eat, drink, or exercise before the test.
- You take medicines such as estrogen, amphetamines, or corticosteroids.
- You don't collect urine for exactly 24 hours.
What To Think About
- A 24-hour urine test is used more often than a cortisol blood test to diagnose Cushing's syndrome. To learn more about a cortisol blood test, see the topic Cortisol in Blood.
- Other tests can help find out if the pituitary gland or adrenal glands are working well. These include the adrenocorticotropic hormone (ACTH) and dexamethasone suppression tests.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerAlan C. Dalkin, MD - Endocrinology
Current as ofNovember 20, 2015