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ACTH Stimulation Test

Published: July 27, 2026Updated: August 25, 2026

The ACTH stimulation test measures the level of cortisol in the blood to assess the functioning of the adrenal glands and diagnose conditions like Addison's disease or Cushing's syndrome.

Quick summary

The ACTH stimulation test evaluates adrenal gland function by measuring cortisol levels.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
μg/dL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche Cortisol, Siemens Cortisol, Cortrosyn Stimulation Test
interpretation: {"text":"Cortisol levels below 18 μg/dL after ACTH stimulation may indicate adrenal insufficiency, such as Addison's disease.","label":"Low Cortisol Levels"}; {"text":"Cortisol levels above 22 μg/dL after ACTH stimulation may suggest Cushing's syndrome or other conditions causing excess cortisol production.","label":"High Cortisol Levels"}

The ACTH stimulation test involves administering a synthetic form of adrenocorticotropic hormone (ACTH) and then measuring the cortisol levels in the blood before and after the injection. This test helps determine if the adrenal glands are functioning properly and can aid in diagnosing adrenal insufficiency or hypercortisolism.

Cortisol is a steroid hormone produced by the adrenal glands in response to ACTH. The test is particularly useful in differentiating between primary and secondary adrenal insufficiency, as well as in evaluating patients with suspected Cushing's syndrome.

Normal cortisol levels post-ACTH stimulation typically range from 18–22 μg/dL. Levels below this range may indicate adrenal insufficiency, while higher levels could suggest Cushing's syndrome or other conditions.

Frequently asked questions

How is the ACTH stimulation test performed?
The test involves drawing blood to measure baseline cortisol, injecting synthetic ACTH, and then drawing more blood to measure cortisol levels at specific intervals.
What are the risks of the ACTH stimulation test?
The test is generally safe, but some people may experience minor side effects like dizziness, nausea, or skin reactions at the injection site.
  1. 1
    ACTH Stimulation TestSource
  2. 2
    Addison's Disease DiagnosisSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy