Adrenal Testing

Test Overview

An adrenocorticotropic hormone test measures the level of adrenocorticotropic hormone (ACTH) in the blood. This test checks for problems with the pituitary gland or the adrenal glands. See an illustration of the pituitary gland.

ACTH is made in the pituitary gland in response to the release of another hormone, called corticotropin-releasing hormone (CRH), by the hypothalamus. In turn, the adrenal glands then make a hormone called cortisol, which helps your body manage stress. Cortisol is needed for life, so its levels in the blood are closely controlled. When cortisol levels rise, ACTH levels normally fall. When cortisol levels fall, ACTH levels normally rise.

Both ACTH and cortisol levels change throughout the day. ACTH is normally highest in the early morning (between 6 a.m. and 8 a.m.) and lowest in the evening (between 6 p.m. and 11 p.m.). ACTH levels may be tested in the morning or evening if your doctor thinks that they are abnormal. Cortisol levels are often measured at the same time as ACTH.

Because ACTH is released in bursts, its levels in the blood can vary from minute to minute. Interpretation of the test results is difficult and often requires the skill of a physician.

Why It Is Done

A test to measure ACTH is done to check for:

A problem with the adrenal glands or pituitary gland. A high level of ACTH and a low level of cortisol (or low ACTH and high cortisol levels) could be caused by a problem with the adrenal glands. Low levels of ACTH and cortisol could be caused by a problem with the pituitary gland.

Overproduction of ACTH. This may be caused by overactive adrenal glands and the release of too much cortisol (one form of Cushing's syndrome).

How To Prepare

You may not be able to eat or drink for 10 to 12 hours before an ACTH test. Your doctor may ask you to eat low-carbohydrate foods for 48 hours before the test. Be sure to ask your doctor if there are any foods that you should not eat.

Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. If you take a medicine, such as a corticosteroid, that could change the test results, you will need to stop taking it for up to 48 hours before the test. Your doctor will tell you exactly how long depending on what medicine you take.

Do not exercise for 12 hours before this test.

Try to avoid emotional stress for 12 hours before the test.

Collecting the blood sample at the right time is often important. Your blood will be drawn in the morning if your doctor wants a peak ACTH level. Your blood will be drawn in the evening if your doctor wants a low (trough) ACTH level.

Talk to our 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.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.


An adrenocorticotropic hormone test measures the level of adrenocorticotropic hormone (ACTH) in the blood.

Results of an ACTH test are usually available in 4 to 6 days.


Normal values vary widely from lab to lab.

Normal ACTH levels
6 a.m. to 8 a.m.

Less than 80 pg/mL or less than 18 pmol/L

6 p.m. to 11 p.m.

Less than 50 pg/mL or less than 11 pmol/L

High values

High levels of ACTH may be caused by:

  • Emotional or physical stress (such as recent surgery or severe pain).
  • Diseases such as Addison's disease, Cushing's disease, or a tumor in the adrenal glands or the pituitary gland.

Low values

Low levels of ACTH may be caused by:

  • Damage to the pituitary gland from surgery, radiation, stroke, head injury, or a tumor.
  • An increased amount of cortisol from a tumor in the adrenal glands (Cushing's syndrome).
ACTH and cortisol levels in specific conditions
Condition ACTH Cortisol

Cushing's disease



Adrenal tumor (Cushing's syndrome)



ACTH made outside the pituitary gland



Addison's disease






What To Think About

  • The interpretation of the ACTH test is complicated because many things can change the results. Blood must be collected in special tubes, placed on ice, and processed quickly. The time of day when the blood is drawn can also change the results. ACTH test results should be compared to medical information gathered from other tests, especially the blood cortisol level. 
  • Inferior petrosal sinus sampling is a test that measures the amount of ACTH from a channel (inferior petrosal sinus) near the pituitary gland. This test may be done along with an ACTH blood test when the levels of both ACTH and cortisol are high. It is used to tell the difference between ACTH made by the pituitary gland and ACTH made somewhere else in the body. This test may only be available at large medical centers.

Begin Your Journey to Adrenal testing with Patients Medical

Our job at Patients Medical is to listen, to connect the dots between a patient's medical history, symptoms, and their underlying causes. Patients Medical is a superb place for women and men to secure integrative and holistic health care from providers who give personalized care, partner with the patient to focus on the root cause of their illness, support their recovery, and help them maintain good health.

To make an appointment with one of our physicians, please call us at 1-212-794-8800. We look forward to hearing from you.


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