ACTH Stimulation Test

Do I need to do anything to prepare for an ACTH stimulation test?

You may need to limit activities and eat foods that are high in carbohydrates 12 to 24 hours before your ACTH stimulation test. You may also need to fast for six hours before the test, which means not eating or drinking anything except water. Your healthcare provider may have you temporarily stop taking certain medications that can interfere with the cortisol blood test.

Since cortisol levels normally vary throughout the day, peaking in the morning, you may need to have your ACTH stimulation test in the morning to minimize the risk of a false-positive result.

In any case, your provider will give you specific instructions for your ACTH stimulation test. Be sure to follow them.

How does an ACTH stimulation test work?

The basic steps of an ACTH stimulation test include:

1. A phlebotomist will take a blood sample from a vein in your arm for an initial, baseline level of your cortisol levels and potentially other substances in your blood.
2. A nurse will give you an injection of synthetic ACTH (cosyntropin) through a shot into your muscle. The synthetic ACTH acts like your body’s natural ACTH and stimulates your adrenal glands to produce cortisol.
3. A phlebotomist will take a blood sample from your vein again to measure your cortisol levels after a specified amount of time — usually 30 minutes and 60 minutes.
4. A phlebotomist will send your blood samples to a laboratory for testing.

What should I expect during an ACTH stimulation test?

You can expect to experience the following during a blood test, or blood draw:

• You’ll sit in a chair, and a healthcare provider will check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.
• Once they’ve located a vein, they’ll clean and disinfect the area.
• They’ll then insert a small needle into your vein to take a blood sample. This may feel like a small pinch.
• After they insert the needle, a small amount of blood will collect in a test tube.
• Once they have enough blood to test, they’ll remove the needle and hold a cotton ball or gauze on the site to stop the bleeding.
• They’ll place a bandage over the site.

When a nurse gives you a shot injection of cosyntropin, it’ll likely be in your upper arm near your shoulder. The injection may cause moderate pain or stinging, but this will be temporary.

What should I expect after my ACTH stimulation test?

After a healthcare provider has collected your blood samples, they’ll send them to a laboratory for testing. Once the test results are back, your healthcare provider will share the results with you.

What are the risks of an ACTH stimulation test?

Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having blood tests. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.

When should I know the results of my ACTH stimulation test?

It may take one week to get your ACTH stimulation test results back. This is because it requires careful interpretation by your provider once the laboratory processes the samples.