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Fasting Cortisol AM

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

Fasting cortisol AM measures the level of cortisol, a hormone produced by the adrenal glands, in the blood during the morning hours after fasting. It is often used to assess adrenal function and diagnose conditions like Cushing's syndrome or Addison's disease.

Quick summary

Fasting cortisol AM is a diagnostic test for adrenal function and related disorders.

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, Abbott Cortisol
interpretation: {"text":"Levels below 5 μg/dL may indicate adrenal insufficiency, such as in Addison's disease or hypopituitarism.","label":"Low Levels"}; {"text":"Levels above 25 μg/dL may suggest Cushing's syndrome, ectopic ACTH production, or adrenal tumors.","label":"High Levels"}

Cortisol is a steroid hormone that plays a crucial role in the body's response to stress, metabolism, and immune function. It is produced by the adrenal glands and follows a diurnal pattern, with levels typically peaking in the morning.

Measuring fasting cortisol AM levels helps in evaluating the functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Abnormal levels can indicate overproduction or underproduction of cortisol, which may be associated with various endocrine disorders.

The reference range for fasting cortisol AM is typically between 5–25 μg/dL. Levels outside this range may require further investigation to determine the underlying cause.

Frequently asked questions

What is the ideal time to test fasting cortisol AM?
The test should be performed in the morning, ideally between 8:00 and 9:00 AM, as cortisol levels naturally peak during this time.
Can stress affect fasting cortisol AM levels?
Yes, acute or chronic stress can elevate cortisol levels, potentially affecting test results.
  1. 1
    Mayo Clinic: Cortisol TestSource
  2. 2
    National Institute of Diabetes and Digestive and Kidney Diseases: Adrenal Insufficiency & Addison's DiseaseSource

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