Cortisol in Blood

A cortisol test is done to measure the level of the Reference hormone Opens New Window cortisol in the blood. The cortisol level may show problems with the Reference adrenal glands Opens New Window or Reference pituitary gland Opens New Window. Cortisol is made by the Reference adrenal glands Opens New Window Reference Opens New Window. Cortisol levels go up when the Reference pituitary gland Opens New Window Reference Opens New Window releases another hormone called Reference adrenocorticotropic hormone Opens New Window (ACTH).

Cortisol has many functions. It helps the body use sugar (glucose) and fat for energy (Reference metabolism Opens New Window), 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 Reference Cushing's syndrome Opens New Window.

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.

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