A cortisol test is done to measure the level
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
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.
Why It Is Done
cortisol test is done to find problems of the
pituitary gland or adrenal glands, such as making too much or too little
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.
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
nonprescription and prescription medicines you
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?).