Is my Cortisol normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Cortisol level?
Cortisol is the primary stress hormone produced by the adrenal glands, following a diurnal pattern — highest in the morning (6-8 AM) and lowest at midnight. Normal morning cortisol is 6-18 µg/dL. Chronically elevated cortisol (Cushing syndrome) causes weight gain, muscle wasting, and immune suppression. Critically low cortisol (Addison disease, adrenal insufficiency) is life-threatening. Even subclinical cortisol dysregulation — such as a flattened diurnal curve — is associated with accelerated biological aging, visceral fat accumulation, and impaired hippocampal neurogenesis.
| Range | Values |
|---|---|
| Standard Reference | 6–18 µg/dL |
| High Risk | > 23 µg/dL |
| Low Risk | < 3 µg/dL |
What causes abnormal Cortisol levels?
High cortisol can be caused by chronic psychological stress, sleep deprivation, overtraining, Cushing syndrome (pituitary adenoma, adrenal tumor, or ectopic ACTH production), long-term corticosteroid medications (prednisone, dexamethasone), excessive alcohol use, and severe obesity. Low cortisol is caused by Addison disease (autoimmune adrenal destruction), pituitary insufficiency, abrupt withdrawal from long-term corticosteroids, and adrenal hemorrhage.
When should you see a doctor?
See your doctor if morning cortisol is below 3 µg/dL (possible adrenal insufficiency — potentially life-threatening) or above 23 µg/dL (possible Cushing syndrome). Also consult if you experience unexplained weight gain (especially central obesity), muscle weakness, easy bruising, or persistent fatigue with salt cravings.
Cortisol and longevity
The cortisol diurnal curve is a powerful biomarker of stress resilience and biological aging. A healthy pattern shows a sharp morning peak (cortisol awakening response) followed by steady decline to near-zero at midnight. Chronic stress flattens this curve — blunting the morning peak and elevating nighttime cortisol. This flattened pattern is associated with visceral fat accumulation, hippocampal atrophy (impairing memory and cognition), immune dysregulation, accelerated telomere shortening, and increased all-cause mortality. Cortisol also directly antagonizes testosterone and growth hormone, two anabolic hormones essential for muscle maintenance and tissue repair in aging. Salivary cortisol testing with 4 daily samples provides the most complete picture of HPA axis function.
Where to get a Cortisol test
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Related biomarkers
These biomarkers are often tested alongside Cortisol for a more complete picture.
Frequently asked questions
What is a normal cortisol level?
Why does cortisol timing matter?
What causes high cortisol?
How can I lower cortisol naturally?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.