What is Cortisol?
Cortisol is a glucocorticoid hormone made by the adrenal glands under the control of the pituitary hormone ACTH. It follows a circadian rhythm highest in the morning and lowest at night and helps regulate blood sugar, blood pressure, metabolism, inflammation, and the stress response.
Why it matters
Both excess cortisol (Cushing's syndrome) and deficiency (Addison's disease) are serious. Chronically elevated cortisol from stress is linked to weight gain, poor sleep, high blood pressure, and impaired glucose control.
What it measures
Serum cortisol at a specific time (usually 8 a.m.), since timing is essential given the daily rhythm. Salivary, urine (24-hour), and dexamethasone-suppression testing are used to investigate abnormalities.
Reference & optimal ranges
Reference ranges vary by lab, assay, age, and sex. The ranges below reflect commonly published adult intervals and are for education only always interpret results with the range printed on your own lab report and a clinician.
High cortisol can reflect acute stress, illness, or Cushing's syndrome; chronic elevation harms metabolic and cognitive health.
Common symptoms
- Weight gain (central/abdominal)
- Round face, easy bruising
- High blood pressure
- Poor sleep, anxiety
- Muscle weakness
Potential causes
- Chronic stress
- Cushing's syndrome (adrenal/pituitary tumor)
- Corticosteroid medication
- Acute illness
Low cortisol (adrenal insufficiency) can be life-threatening and requires prompt evaluation.
Common symptoms
- Fatigue and weakness
- Weight loss, low appetite
- Low blood pressure, dizziness
- Salt craving
- Skin darkening (Addison's)
Potential causes
- Addison's disease (adrenal failure)
- Pituitary dysfunction
- Abrupt stop of long-term steroids
How to improve your Cortisol
Lifestyle
Manage chronic stress
Mindfulness, breathing practices, and reducing stressors lower chronically elevated cortisol.
Protect your circadian rhythm
Morning light and a consistent schedule support a healthy cortisol curve.
Nutrition
Limit excess caffeine and alcohol
Both can amplify cortisol responses and disrupt sleep.
Exercise
Moderate exercise, avoid overtraining
Regular activity lowers baseline stress, but excessive training raises cortisol.
Sleep
Prioritize sleep
Sleep deprivation raises evening cortisol; consistent sleep restores the rhythm.
Frequently asked questions
Scientific references
- Cortisol Test Testing.com
- Cortisol Test MedlinePlus, U.S. National Library of Medicine
Educational information, not medical advice. This page is for general education and does not replace diagnosis or treatment by a licensed clinician. Do not start, stop, or change any medication, supplement, or treatment based on this content. Reference and optimal ranges vary between laboratories interpret your results with the range on your own report and a qualified professional.