ACTH Stimulation Test

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ACTH Stimulation Test

ACTH Stimulation Test

Why am I having this test?

The adrenocorticotropic hormone (ACTH) stimulation test is used to measure how well your adrenal glands are working.

What is being tested?

This test checks the levels of cortisol in your blood before and after your adrenal glands are stimulated with ACTH. ACTH is produced by a gland in your brain called the pituitary gland. ACTH stimulates your two adrenal glands, which are located above each kidney.

The adrenal glands produce hormones that are released into the blood. One of these hormones is cortisol. Cortisol helps your body to respond to stress. If your adrenal glands are not working well and are not responding to ACTH properly, the test result will show too little cortisol.

What kind of sample is taken?

Two or more blood samples are required for this test. The samples are usually collected by inserting a needle into a blood vessel.

How do I prepare for this test?

  • Do not eat or drink anything after midnight on the night before the test or as directed by your health care provider. You may continue to drink water up until the time of your test.
  • You may be instructed to avoid certain medicines that can affect cortisol levels, such as those containing estrogen or steroids. Make sure that the health care provider ordering the test is aware of any recent use of steroid hormones, such as prednisone or cortisone injections.
  • Follow any additional instructions as directed by your health care provider.

Tell a health care provider about:

  • Any allergies you have.
  • All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
  • Any blood disorders you have.
  • Any surgeries you have had.
  • Any medical conditions you have.
  • Whether you are pregnant or may be pregnant.

What happens during the test?

This test is usually done in the morning, since your cortisol levels change throughout the day.
  1. The first blood sample will be collected. Cortisol will be measured in this sample to provide your starting (baseline) level.
  2. You will be given cosyntropin by injection or through an IV. Cosyntropin is similar to ACTH and should cause the adrenal glands to release cortisol into the bloodstream.
    • You may feel a slight flush after the cosyntropin is given. This is normal.
  3. One or more blood samples will be taken at specified intervals (30 or 60 minutes after the cosyntropin injection) in order to measure your cortisol levels after the adrenal gland is stimulated.
  4. The test results will be compared to show the amount of cortisol in your blood before and after you were given cosyntropin.

How are the results reported?

Your test results will be reported as values. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, a common reference range is:
  • A baseline cortisol level from 7 mcg/dL to 10 mcg/dL, reaching at least 18 mcg/dL at 60 minutes after stimulation.

What do the results mean?

Results outside the reference range may indicate that you have:
  • Adrenal insufficiency. This can be caused by a problem in the adrenal gland itself (primary adrenal insufficiency or Addison's disease) or by a problem outside the adrenal gland (secondary adrenal insufficiency).
    • Causes of primary adrenal insufficiency include autoimmune inflammation of the adrenal gland, infection involving the adrenal gland, a tumor that has spread to the adrenal gland, and bleeding into the adrenal gland.
    • Causes of secondary adrenal insufficiency include conditions that cause the pituitary gland to function less than normal (hypopituitarism). This may be due to a specific disease involving the pituitary gland or the use of high-dose steroid medications to treat another medical condition.

Other tests may be needed to find the cause of adrenal gland conditions and confirm a diagnosis.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:
  • When will my results be ready?
  • How will I get my results?
  • What are my treatment options?
  • What other tests do I need?
  • What are my next steps?


  • The ACTH stimulation test is used to measure how well your adrenal glands are working.
  • The test has three steps. First, your blood is tested to measure your starting (baseline) cortisol level. Second, you are given cosyntropin to stimulate your adrenal glands to release cortisol. Third, your blood is tested to see how much cortisol is in your blood after stimulation.
  • Results outside the normal range may indicate that you have a condition that affects how well your adrenal glands function.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.