Cortisol is the main stress hormone, made by the adrenal glands. It peaks in the early morning.
- Normal range (adults)
- 6–23 µg/dL (166–635 nmol/L)
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- Serum Cortisol, Cortisol AM, Morning Cortisol
Cortisol normal range
| Group | µg/dLConventional units: US, South Asia | nmol/LSI units: UK, Europe, Australia, international |
|---|---|---|
| Adults | 6–23 | 166–635 |
This range applies to a morning sample (about 7–9 am). Levels are much lower in the evening.
Your report may use either unit system; labs in the Gulf often print both. Ranges also vary slightly between laboratories, so the range printed on your own report is the one to go by.
Why is the Cortisol test done?
It is checked when adrenal underactivity (Addison's disease) or excess (Cushing's syndrome) is suspected.
What does a high Cortisol level mean?
High cortisol can come from stress, illness or steroid medicines. Persistently high levels (Cushing's syndrome) cause weight gain around the middle, a round face, thin skin, easy bruising and high blood pressure or sugar.
Common causes
- Acute stress or illness
- Steroid tablets, inhalers or creams
- Pregnancy or estrogen pills
- Cushing's syndrome (rare)
Diet and lifestyle tips
- Prioritise sleep and stress management
- Limit sugar and salt
- Do not stop steroid medicines suddenly
What does a low Cortisol level mean?
A low morning cortisol can mean the adrenal glands are underactive, causing tiredness, weakness, weight loss, dizziness and salt craving.
Common causes
- Stopping long-term steroid medicines
- Addison's disease (autoimmune)
- Pituitary problems
- Testing late in the day
Diet and lifestyle tips
- Do not restrict salt if your doctor suspects adrenal insufficiency
- Eat regular meals
When should you see a doctor?
A low cortisol with vomiting, severe weakness or fainting is an emergency.
Last updated
This page is for general education and is not a diagnosis. Normal ranges differ between laboratories, so always compare your result with the reference range printed on your own report, and discuss abnormal results with your doctor.