A cortisol level is a blood test that measures the amount of cortisol, a steroid hormone produced by the adrenal cortex.

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:

• Estrogen
• Human-made (synthetic) glucocorticoids, such as prednisone and prednisolone

Drugs that can decrease cortisol measurements include:

• Androgens
• Phenytoin

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.

Cortisol is a steroid hormone released from the adrenal cortex in response to a hormone called ACTH (produced by the pituitary gland).

Cortisol levels are often measured to evaluate how well the pituitary and adrenal glands are working.

Normal values at 8 a.m. are 6 - 23 mcg/dL.

Note: mcg/dL = micrograms per deciliter

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:

• Adrenal tumor
• Cushing's syndrome
• Ectopic ACTH-producing tumors

Lower than normal levels may indicate:

• Addison's disease
• Hypopituitarism

Other conditions under which the test may be performed:

• Acute adrenal crisis
• Ectopic Cushing's syndrome
• Pituitary Cushing's (Cushing's disease)

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.

Stewart PM. The adrenal cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008: chap 14.