Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
The health care provider may ask you to stop taking drugs that can affect the test. Drugs that can increase cortisol measurements include:
- Human-made (synthetic) glucocorticoids, such as prednisone and prednisolone
Drugs that can decrease cortisol measurements include:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
The test is done to check for increased or decreased cortisol production. Cortisol is a steroid hormone released from the adrenal gland in response to ACTH, a hormone from the pituitary gland in the brain.
Cortisol affects many different body systems. It plays a role in:
- Circulatory system
- Immune system
- Metabolism of fats, carbohydrates, and protein
- Nervous system
- Stress responses
Different diseases, such as Cushing's disease and Addison's disease, can lead to either too much or too little production of cortisol. Cortisol levels are often measured to help diagnose these conditions and to evaluate how well the pituitary and adrenal glands are working.
Normal values for a blood sample taken at 8 in the morning are 6 - 23 micrograms per deciliter (mcg/dL).
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
Higher than normal levels may indicate:
Lower than normal levels may indicate:
Other conditions under which the test may be performed:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Normally, cortisol levels rise and fall during the day, repeating on a 24-hour cycle (diurnal variation). Highest levels are at about 6 - 8 a.m. and lowest levels are at about midnight.
Physical and emotional stress can increase cortisol levels, because during the normal stress response, the pituitary gland increases its release of ACTH.
Higher than normal cortisol levels are expected in women who take estrogen or birth control pills.