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Normal Cortisol Levels — How to Test and What Results Mean (2026)
What are normal cortisol levels? How to test cortisol, what elevated or low levels mean, and when to see a doctor. Updated January 2026.
📅 Updated January 2026⏱ 8 min read👤 Dr. Priya Sharma, MD✓ Medically Reviewed
Key Takeaways
- Normal morning cortisol is 200–700 nmol/L (UK) or 7–28 mcg/dL (USA)
- Cortisol has a diurnal rhythm — highest at 8am, lowest at midnight
- Cushing's syndrome (chronically very high cortisol) and Addison's disease (very low) are serious medical conditions
- Chronically mildly elevated cortisol from lifestyle stress is real but not diagnosed by a standard blood test
- Saliva cortisol at four time points gives a more complete picture than a single blood test
Cortisol's Daily Rhythm (Diurnal Pattern)
Cortisol is not constant — it follows a predictable 24-hour pattern governed by the circadian clock. Understanding this rhythm is essential for interpreting cortisol measurements.
| Time | Normal Cortisol Level | Notes |
|---|
| 6–8am (waking) | 200–700 nmol/L | Cortisol Awakening Response — peaks 30–45 min after waking |
| 8–9am (standard test) | 200–700 nmol/L | Standard clinical measurement time |
| 12pm (noon) | 150–400 nmol/L | Declining through the morning |
| 4pm (afternoon) | 50–300 nmol/L | Approximately half morning level |
| 11pm–midnight | Below 50 nmol/L | Near nadir — should be very low |
200–700
Normal morning cortisol nmol/L (UK range)
30–45 min
After waking — cortisol peaks (Cortisol Awakening Response)
4 points
Optimal number of daily measurements for full picture
How Cortisol Is Tested
Serum (Blood) Cortisol
The standard NHS test. Most informative when collected at 8–9am (peak). A low result (<100 nmol/L at 8am) suggests possible adrenal insufficiency (Addison's disease). A high result (>800 nmol/L) suggests possible Cushing's syndrome — requiring further confirmation tests.
Salivary Cortisol (Multiple Points)
Saliva testing at 4 time points (waking, 12pm, 4pm, bedtime) captures the full diurnal cortisol rhythm. This is more useful than a single blood test for assessing lifestyle-related cortisol dysregulation — poor sleep, chronic stress, adrenal fatigue patterns. Available through private testing companies.
24-Hour Urinary Cortisol
Measures total cortisol output over 24 hours. Used when Cushing's syndrome is suspected. Above 250 nmol/24hr (UK) is suspicious; above 350 nmol/24hr is highly suspicious and requires further investigation.
ℹ️ Cushing's vs Addison's — Key Signs
Cushing's syndrome (too much cortisol): Central weight gain, moon face, purple stretch marks, easy bruising, high blood pressure, buffalo hump (fat deposit at base of neck), diabetes.
Addison's disease (too little cortisol): Profound fatigue, weight loss, low blood pressure, skin darkening (particularly in skin folds), salt cravings, nausea. Both are serious conditions requiring urgent medical investigation and treatment.
Frequently Asked Questions
What is a normal cortisol level?▼
Normal morning (8–9am) serum cortisol: 200–700 nmol/L (UK) or 7–28 mcg/dL (USA). Normal 4pm cortisol: 50–300 nmol/L (should be about half morning level). Normal midnight cortisol: below 50 nmol/L. A single morning measurement outside these ranges should be repeated before further investigation.
Can stress cause high cortisol on a blood test?▼
Acute psychological stress before a blood test can elevate cortisol readings temporarily. This is one reason clinical cortisol testing is often repeated on different days. Chronically elevated cortisol from lifestyle stress (work pressure, relationship stress) rarely produces cortisol levels high enough to be detected as abnormal on a standard blood test — the elevations are subtle and within the 'normal' range.
How do I get a cortisol test?▼
In the UK: Request an early morning cortisol blood test from your GP if you have symptoms suggesting Cushing's or Addison's syndrome. Private saliva cortisol testing (DUTCH test, ZRT laboratory) tests cortisol at 4 time points throughout the day — better for detecting circadian rhythm disruption. Consumer saliva tests are available online but require careful interpretation.
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⚕️ Medical Disclaimer: For informational purposes only. Not a substitute for professional medical advice.
PS
Dr. Priya Sharma, MD
WellCalc Medical Contributor
All articles reviewed by qualified healthcare professionals following NHS, AHA, and WHO guidelines.