Definition

The ACTH test measures the level of adrenocorticotropic hormone (ACTH) in the blood. ACTH is a hormone released from the pituitary gland at the base of the brain.

Alternative Names

Serum adrenocorticotropic hormone; Adrenocorticotropic hormone; Highly-sensitive ACTH

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Your health care provider will likely ask you to have the test done early in the morning. This is important because the ACTH level varies throughout the day.

You may also be told to stop taking medicines that can affect the test results. These medicines include glucocorticoids such as prednisone, hydrocortisone, or dexamethasone. Do not stop these medicines unless instructed by your provider.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

The main function of ACTH is to regulate the glucocorticoid (steroid) hormone cortisol. Cortisol is released by the adrenal gland. It regulates blood pressure, blood sugar, the immune system, and the response to stress.

This test can help find the causes of certain hormone problems.

Normal Results

Normal values for a blood sample taken early in the morning are 9 to 52 pg/mL (2 to 12 pmol/L).

Normal value ranges may vary slightly among different labs. Some labs use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

A higher-than-normal level of ACTH may indicate:

• Adrenal glands not producing enough cortisol (Addison disease)
• Adrenal glands not producing enough hormones (congenital adrenal hyperplasia)
• One or more of the endocrine glands are overactive or have formed a tumor (multiple endocrine neoplasia type I)
• Pituitary is making too much ACTH (Cushing disease), which is usually caused by a non-cancerous tumor of the pituitary gland
• Rare type of tumor (lung, thyroid, or pancreas) making too much ACTH (ectopic Cushing syndrome)

A lower-than-normal level of ACTH may indicate:

• Glucocorticoid medicines are suppressing ACTH production (most common)
• Pituitary gland not producing enough hormones, such as ACTH (hypopituitarism)
• Tumor of the adrenal gland that produces too much cortisol
• A normal response after taking the low-dose dexamethasone suppression test

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood 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 lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Auchus RJ, Pandey CEF. The adrenal cortex. In: Melmed S, Auchus, RJ, Goldfine AB, Rosen CJ, Kopp PA, eds. Williams Textbook of Endocrinology. 15th ed. Philadelphia, PA: Elsevier; 2025:chap 13.

Guber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.

Melmed S, Casanueva FF. Pituitary adenomas and masses. In: Melmed S, Auchus, RJ, Goldfine AB, Rosen CJ, Kopp PA, eds. Williams Textbook of Endocrinology. 15th ed. Philadelphia, PA: Elsevier; 2025:chap 7.

Nieman LK. Adrenal cortex. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 208.

Weiss RE. Anterior pituitary. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 205.