Adrenocorticotropic Hormone (ACTH) Test
Reviewed
This test measures the level of adrenocorticotropic hormone (ACTH) in your blood. ACTH is a hormone that tells your adrenal glands to produce cortisol, which affects many body functions. The test is used to help diagnose and monitor conditions that cause too much or too little cortisol, such as Cushing's disease, Addison disease, or hypopituitarism. Your provider will compare your ACTH and cortisol levels to interpret the results.
Preparation and collection
Your provider will give you specific instructions. You may need to fast (not eat or drink) for several hours before the test. Blood samples are often taken early in the morning when ACTH levels are highest. You may need to stop taking certain medicines before the test, but do not stop any medication unless your provider tells you to.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Results are not sufficient for diagnosis on their own.
- Your healthcare provider will interpret your ACTH and cortisol levels together.
- Additional tests are often needed to confirm the specific cause of abnormal results.
What to do next
Your provider may recommend additional tests such as a CT or MRI scan, or an ACTH stimulation test to further evaluate the cause of abnormal results.
Evidence source
U.S. National Library of Medicine: Adrenocorticotropic Hormone (ACTH) Test