ACTH Blood Test: What High and Low ACTH Levels Mean
Order ACTH Test | Adrenocorticotropic HormoneQuick Answer
An ACTH test measures adrenocorticotropic hormone, the pituitary signal that tells your adrenal glands to make cortisol. This guide explains normal ACTH levels, what high or low results can mean, and how to order the test directly.
Key Takeaways
- ACTH (adrenocorticotropic hormone) is made by the pituitary gland and tells the adrenal glands to release cortisol.
- A typical normal ACTH range is about 7 to 63 pg/mL, but reference ranges vary by laboratory and collection time.
- High ACTH often points to primary adrenal insufficiency, where the adrenal glands underproduce cortisol.
- Low ACTH usually suggests an underactive pituitary or excess cortisol coming from another source.
- ACTH is usually interpreted together with a cortisol test, and sometimes with an AM/PM cortisol pattern.
- Direct-access ACTH testing typically costs between about $50 and $100.
What Is an ACTH Test?
An ACTH test measures adrenocorticotropic hormone, a signaling hormone made by the pituitary gland at the base of the brain. ACTH travels through the blood to the adrenal glands, which sit on top of the kidneys, and tells them to produce cortisol. Cortisol helps regulate blood sugar, blood pressure, the immune response, and the body's reaction to stress.
ACTH is sometimes called corticotropin. It is released in pulses, with the largest pulses in the early morning just before waking, which is why collection time matters so much. Because ACTH and cortisol work as a feedback loop, an ACTH blood test is rarely read on its own. Clinicians usually compare it with a cortisol level, and sometimes with an AM/PM cortisol pattern, to see whether the adrenal glands are responding normally to the pituitary's signal.
Why an ACTH Test Is Ordered
An ACTH test is most often ordered when a cortisol result is abnormal or when a doctor suspects a hormone disorder involving the adrenal or pituitary glands. Common reasons include:
- Fatigue, weight loss, low blood pressure, or darkening of the skin that may suggest adrenal insufficiency
- Weight gain around the trunk, easy bruising, or high blood pressure that may suggest excess cortisol
- An abnormal cortisol result that needs to be explained
- Monitoring a known pituitary or adrenal condition
- Investigating low sodium, high potassium, or unexplained low blood sugar
Doctors also order ACTH when a person has unexplained low blood pressure, salt cravings, or repeated episodes of low blood sugar. In those cases the goal is to find out whether the adrenal glands themselves are failing or whether the pituitary is not sending a strong enough signal.
Normal ACTH Levels
A typical reference range for ACTH is about 7 to 63 pg/mL (roughly 1.6 to 13.9 pmol/L). Some laboratories use slightly different limits, and ranges can shift with the time of day and the assay method. Always compare your result with the range printed on your own report.
| Result | Typical range | What it can suggest |
|---|---|---|
| Normal | About 7 to 63 pg/mL | Pituitary and adrenal signaling appear balanced |
| High | Above the lab's upper limit | The adrenal glands may be underproducing cortisol |
| Low | Below the lab's lower limit | The pituitary may be underactive, or cortisol is high from another cause |
Some laboratories report ACTH in picomoles per liter instead of picograms per milliliter, so the numbers look very different even when the result means the same thing. Check the unit on your report before comparing it with any general range you read online.
What High ACTH Means
A high ACTH level usually means the pituitary is working hard to push the adrenal glands, which are not making enough cortisol. This pattern is typical of primary adrenal insufficiency, also called Addison disease. Other causes include congenital adrenal hyperplasia and, less often, a pituitary tumor that produces too much ACTH.
Rarely, a tumor outside the pituitary can make ACTH, which is called ectopic ACTH production. That cause is uncommon, but it is one reason an unexpected high result is investigated carefully. High ACTH is interpreted with a low or low-normal cortisol, and when both hormones are high the picture points toward excess cortisol rather than adrenal failure.
What Low ACTH Means
A low ACTH level often points to a problem in the pituitary gland, which may be underactive for several reasons. It can also occur when the body is exposed to high levels of cortisol from an adrenal tumor or from long-term steroid medicines, because the extra cortisol suppresses ACTH through feedback.
Medicines that contain steroids are a common reason for a suppressed ACTH, since they act like cortisol in the body and the pituitary responds by lowering its signal. Because the causes differ so much, a low ACTH is always read alongside cortisol, and sometimes with imaging or additional hormone tests.
How to Order an ACTH Test
You can order an ACTH test directly through a direct-access lab service without a physician's order or insurance. Choose the test online, pay the listed price, and visit a local collection site for a blood draw. The sample is processed at a CLIA-certified laboratory, and results are usually available within a few business days.
Because ACTH is time-sensitive, ask about the collection window when you book. Most sites schedule ACTH draws in the early morning so the result can be compared with the standard reference range. If you take steroid medicines, tell the ordering service, since that can affect the result and how it is interpreted. Bring a list of your current medicines to the collection site.
How Much Does an ACTH Test Cost?
Direct-access ACTH testing typically costs between about $50 and $100. The price depends on the laboratory and whether ACTH is bundled with a cortisol test or a broader hormone panel. Prices are usually shown before you order, and no insurance is required.
Frequently Asked Questions
What is a normal ACTH level?
A typical normal ACTH range is about 7 to 63 pg/mL, though reference ranges vary by laboratory and by the time of day the sample is drawn.
What does high ACTH mean?
High ACTH often means the adrenal glands are not making enough cortisol, so the pituitary increases its signal. It is usually interpreted with a cortisol result.
What does low ACTH mean?
Low ACTH can point to an underactive pituitary or to high cortisol from another source. It is read together with cortisol and sometimes other hormone tests.
Do I need to fast for an ACTH test?
Fasting is not usually required. Morning collection is preferred because ACTH follows a daily rhythm and is highest early in the day.
Can I order an ACTH test without a doctor?
Yes. Direct-access lab testing lets you order ACTH online and visit a local collection site without a physician's order or insurance.
How long do ACTH results take?
Most direct-access ACTH results are available within a few business days after the blood draw.
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This guide is reviewed for sourcing accuracy against the references listed above. It is educational information, not medical advice. Always consult a qualified healthcare provider about your own results and care.
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Order ACTH Test | Adrenocorticotropic HormoneReviewed by the LabAppointments Editorial Team
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