Cortisol
Cortisol is the main glucocorticoid hormone, released by the adrenal glands in response to ACTH and following a diurnal rhythm that peaks in the morning. It mobilizes glucose, modulates immune function, and supports blood pressure. Chronic elevation is seen in Cushing syndrome and severe stress, while persistently low morning cortisol suggests adrenal insufficiency.
Units: µg/dL; some labs report nmol/L (nmol/L = µg/dL × 27.6). Check the units on your report before comparing to any range here.
Optimal range: who says what
Institutions, researchers and practitioners draw the line in different places. Each position is listed with who holds it and, where a document states it, a link. How we verify ranges.
- Institution or studyMorning ≥15.5 μg/dL excludes adrenal insufficiencySheikh-Ahmad et al. 2026 (BMC Endocr Disord)A diagnostic threshold, not an optimal target: every patient at or above 15.5 μg/dL (428 nmol/L) passed the stimulation test, and none below 3 μg/dL did
- Lab reference interval5-25 µg/dL at 8 AM (MedlinePlus)What a lab report flags against. A lab interval is not an optimal target.
17 of 21 itemized panels
Stress & Adrenal Function
What is Cortisol?
Cortisol is the primary stress hormone produced by your adrenal glands in response to physical or psychological stress, low blood sugar, inflammation, or circadian rhythm. It's often called the "fight-or-flight" hormone, but this oversimplifies its role. Cortisol is essential for survival: it regulates metabolism, blood pressure, immune function, and helps your body respond to stress. Problems arise when cortisol is chronically elevated (from chronic stress, Cushing's syndrome) or deficient (adrenal insufficiency).
Cortisol follows a strong circadian rhythm. It's highest in the morning (peak around 8 AM) to help you wake up and get moving, then gradually declines throughout the day, reaching its lowest point around midnight to allow sleep. Disruption of this rhythm—high cortisol at night, low cortisol in the morning, or chronically elevated levels—is associated with insomnia, weight gain, insulin resistance, immune dysfunction, and accelerated aging.
A single cortisol measurement isn't very informative without context of timing. Morning cortisol should be tested between 7-9 AM. A 4-point salivary cortisol test (morning, noon, evening, bedtime) better captures the daily rhythm and is useful for assessing chronic stress, adrenal dysfunction, or HPA axis dysregulation. Serum cortisol is standard for diagnosing Cushing's or Addison's disease, while salivary cortisol is better for functional assessment.
Why Cortisol Balance Matters for Longevity
- Metabolic regulation: Cortisol raises blood sugar by promoting gluconeogenesis. Chronic elevation causes insulin resistance, visceral fat accumulation, type 2 diabetes.
- Immune function: Physiologic cortisol is anti-inflammatory and modulates immune response. Too high suppresses immunity (infections, poor wound healing); too low causes autoimmune flares.
- Bone density: Chronic high cortisol increases bone resorption and decreases bone formation, leading to osteoporosis.
- Muscle mass: Elevated cortisol is catabolic, breaking down muscle protein for glucose. Chronic stress accelerates sarcopenia.
- Sleep and circadian rhythm: Cortisol should be low at night to allow deep sleep. High nighttime cortisol causes insomnia and disrupts recovery.
- Longevity: Chronic cortisol elevation accelerates aging, shortens telomeres, and increases mortality from cardiovascular disease and metabolic syndrome.
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: Plasma cortisol and prognosis of patients with acute myocardial infarction (Jutla et al., 2014); Complementary and incremental mortality risk prediction by cortisol and aldosterone in chronic heart failure (Güder et al., 2007); Urinary cortisol and six-year risk of all-cause and cardiovascular mortality (Vogelzangs et al., 2010). No single paper sets these cutoffs; for attributed targets see who says what.
Optimal (Morning 7-9 AM)10-20 mcg/dL▼
- Healthy morning cortisol
- Peak should occur within 30 min of waking (cortisol awakening response)
Optimal (Evening/Bedtime)<5 mcg/dL▼
Cortisol should be low at night to allow restful sleep and overnight recovery.
Suboptimal (Morning)5-10 mcg/dL▼
Low morning cortisol suggests blunted cortisol awakening response, adrenal dysfunction, or chronic stress/burnout.
High (Morning)>25 mcg/dL▼
- Elevated morning cortisol
- May indicate acute stress, Cushing's syndrome, or HPA axis dysregulation
- Retest with dexamethasone suppression test if persistently high
What raises or lowers Cortisol
Causes of high Cortisol
- Cushing's syndrome: Excess cortisol from pituitary adenoma (Cushing's disease), adrenal tumor, ectopic ACTH production (small cell lung cancer), or exogenous steroids.
- Chronic stress: Psychological stress, overtraining, sleep deprivation chronically activate HPA axis.
- Severe depression: Major depressive disorder often associated with HPA axis dysregulation and elevated cortisol.
- Alcoholism: Chronic alcohol use disrupts HPA axis, raising cortisol.
- Obesity: Visceral fat produces cortisol locally and amplifies systemic cortisol response.
- Obstructive sleep apnea: Intermittent hypoxia and sleep fragmentation raise cortisol.
- Medications: Estrogen (oral contraceptives, HRT) increases cortisol-binding globulin, raising total cortisol.
Causes of low Cortisol
- Primary adrenal insufficiency (Addison's disease): Autoimmune destruction of adrenal cortex (most common in developed countries). Can't produce cortisol or aldosterone.
- Secondary adrenal insufficiency: Pituitary or hypothalamic failure (tumor, surgery, radiation, Sheehan syndrome) causes low ACTH→low cortisol.
- Chronic exogenous steroid use: Long-term prednisone/dexamethasone suppresses HPA axis. If stopped abruptly, adrenal glands can't produce cortisol (iatrogenic adrenal insufficiency).
- Adrenal hemorrhage: Waterhouse-Friderichsen syndrome (meningococcal sepsis), trauma.
- Chronic stress and burnout: Prolonged HPA axis activation may lead to blunted cortisol response (controversial "adrenal fatigue" concept).
- Medications: Ketoconazole, etomidate, megestrol can suppress cortisol production.
Symptoms when Cortisol is high or low
When high
- Weight gain, especially abdominal/visceral fat
- Moon face, buffalo hump (fat redistribution)
- Muscle weakness, muscle wasting (especially proximal muscles)
- Thin skin, easy bruising, purple striae (stretch marks)
- Insomnia, difficulty falling or staying asleep
- High blood pressure
- High blood sugar, insulin resistance, type 2 diabetes
- Osteoporosis, fractures
- Mood changes: Anxiety, irritability, depression
- Poor wound healing, frequent infections
- Irregular menstrual periods (women)
- Erectile dysfunction (men)
Chronic elevation of cortisol drives metabolic syndrome, visceral obesity, insulin resistance, bone loss, and immune suppression.
When low
- Fatigue, exhaustion, low energy (especially morning)
- Difficulty waking up, non-restorative sleep
- Low blood pressure, dizziness upon standing (orthostatic hypotension)
- Salt cravings
- Weight loss, loss of appetite
- Hypoglycemia, low blood sugar episodes
- Muscle weakness, joint pain
- Darkening of skin (hyperpigmentation in Addison's disease)
- Depression, low mood, apathy
- Frequent infections (impaired immune function)
Low cortisol <5 mcg/dL in morning suggests adrenal insufficiency (Addison's disease or secondary insufficiency). This is a medical emergency if severe.
How to move Cortisol
Effect sizes (how much something moves the marker) appear only where the paper cited under the item states them. Talk to your clinician before starting or changing any medication or supplement.
Manage Chronic Stress (Most Common Cause of Cortisol Dysregulation)
- Meditation and mindfulness: 10-20 min daily meditation has lowered cortisol in some trials. Apps: Headspace, Calm, Insight Timer.
- Deep breathing: 4-7-8 breathing (inhale 4 sec, hold 7 sec, exhale 8 sec) activates parasympathetic nervous system, lowering cortisol.
- Sleep optimization: 7-9 hours nightly. Sleep deprivation raises cortisol. Prioritize consistent sleep/wake times, dark room, cool temp.
- Exercise (but not too much): Moderate exercise lowers cortisol. Overtraining (>90 min high-intensity daily) raises cortisol chronically.
- Social connection: Loneliness and social isolation chronically elevate cortisol. Prioritize relationships, community.
Adaptogenic Herbs (Moderate Evidence)
- Ashwagandha: In a 60-day placebo-controlled trial of 64 chronically stressed adults, a root extract taken twice daily lowered serum cortisol compared with placebo (Chandrasekhar 2012). KSM-66 and Sensoril are well-studied extracts.
- Rhodiola rosea: 200-600 mg/day may reduce stress-induced cortisol spikes and improve mental performance under stress.
- Phosphatidylserine: 300-800 mg/day may blunt exercise-induced cortisol elevation.
- Holy basil (tulsi): 300-600 mg/day may reduce cortisol and stress markers.
- L-theanine: 200-400 mg/day (from green tea or supplement) promotes relaxation without sedation, may modulate cortisol response.
Nutritional Support
- Vitamin C: 1-2 g/day. Adrenal glands have highest vitamin C concentration in body. Vitamin C supplementation blunts cortisol response to stress.
- Magnesium: 400 mg/day. Deficiency exacerbates stress response and cortisol elevation.
- Omega-3 fatty acids: 2-3 g/day EPA+DHA reduces inflammation and may lower cortisol.
- Avoid excessive caffeine: >400 mg caffeine (4 cups coffee) can elevate cortisol, especially if consumed late in day.
Treat Adrenal Insufficiency (if very low cortisol)
- Primary adrenal insufficiency (Addison's disease): Autoimmune destruction of adrenal cortex. Requires lifelong hydrocortisone replacement (15-25 mg/day in divided doses) + fludrocortisone for aldosterone replacement.
- Secondary adrenal insufficiency (pituitary failure): Requires hydrocortisone but not fludrocortisone.
- Adrenal crisis prevention: Patients on steroid replacement need higher "sick-day" doses during illness, surgery, or major stress, set by their endocrinologist, to prevent life-threatening adrenal crisis.
Evaluate and Treat Cushing's Syndrome (if persistently high)
If morning cortisol >25 mcg/dL or loss of circadian rhythm (high at night), evaluate for Cushing's:
- 24-hour urinary free cortisol (elevated in Cushing's)
- Late-night salivary cortisol (elevated in Cushing's)
- Dexamethasone suppression test (cortisol fails to suppress in Cushing's)
- If confirmed, determine cause: Pituitary adenoma (Cushing's disease), adrenal tumor, or ectopic ACTH production. Treatment: surgery, medications (ketoconazole, metyrapone), or radiation.
When to retest
- Morning cortisol (7-9 AM): Baseline to assess adrenal function and circadian rhythm. Compare with the lab interval and the thresholds in who says what above.
- If very low (<5 mcg/dL): Perform ACTH stimulation test to confirm adrenal insufficiency.
- If very high (>25 mcg/dL): Retest and consider dexamethasone suppression test, 24-hour urinary free cortisol, late-night salivary cortisol to evaluate for Cushing's.
- 4-point salivary cortisol: Morning, noon, evening, bedtime. Best for assessing circadian rhythm and chronic stress. Look for blunted morning rise or elevated nighttime levels.
- If treating adrenal insufficiency: Monitor for adequate replacement and stress-dose adjustments. Retest during illness.
- If optimizing stress management: Retest 3-6 months after implementing lifestyle changes (meditation, sleep, adaptogens) to assess improvement in cortisol rhythm.
Scientific Evidence
Flatter Daily Cortisol Slopes and Health
A meta-analysis of 80 studies found that a flatter fall in cortisol from morning to evening was associated with poorer health (average r = 0.147) in 10 of 12 mental and physical outcome types, most strongly for immune and inflammation outcomes (r = 0.288). The authors note a flat slope may be a marker of disease as well as a cause.
Chronic Stress and Cellular Aging
In healthy premenopausal women, higher perceived and chronic psychological stress was associated with higher oxidative stress, lower telomerase activity, and shorter telomeres. Women with the highest perceived stress had telomeres shorter by the equivalent of at least a decade of aging. The study measured stress, not cortisol.
Source: Accelerated telomere shortening in response to life stress.
Diagnosing Cushing's Syndrome
The Endocrine Society recommends first excluding glucocorticoid medication, then starting with one high-accuracy test: urine free cortisol, late-night salivary cortisol, or a 1 mg overnight or 2 mg 48-hour dexamethasone suppression test. An abnormal result should be followed by a second test under an endocrinologist.
Source: The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline.
Which Providers Test Cortisol?
Cheapest: Mito Health at $297/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
17 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $297 | 100+ | $2.97 | |
 Superpower | $349 | 100+ | $3.49 |
| $349 | 75+ | $4.65 | |
 WHOOP Advanced Labs | $349 | 65 | $5.37 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $375 | 108 | $3.47 | |
| $449 | 83 | $5.41 | |
| $495 | 80+ | $6.19 | |
| $499 | 100+ | $4.99 | |
| $700 | 138 | $5.07 | |
| $829 | 54 | $15.35 | |
| $895 | 100+ | $8.95 | |
| $996 | 59 | $16.88 | |
| $1188 | 70+ | $16.97 | |
| $1198 | 40+ | $29.95 | |
| $1950 | 130+ | $15.00 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
4 itemized panels do not include Cortisol
Labcorp OnDemand · Marek Health Base · Empirical Health · Oura Health Panels
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Cortisol. Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Cortisol
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
- A Deep Dive Into How To Interpret The Results Of Your Blood Testing
- Cortisol Decoded: The Myths & Truths About A Hormone Crucial To Your Health
- 7 Signs Your Cortisol and Adrenals Are Broken
- Why Is My Cortisol High Even Though I'm Doing Everything Right? The DUTCH Test
- Best Of Hormone Health
- How to Uncover Hidden Hormone Imbalances
Frequently Asked Questions
What is the optimal range for Cortisol?
Published position: Morning ≥15.5 μg/dL excludes adrenal insufficiency (Sheikh-Ahmad et al. 2026 (BMC Endocr Disord)). Lab reference interval: 5-25 µg/dL at 8 AM (MedlinePlus). That is what a lab report flags against, not an optimal target.
Which blood test providers include Cortisol?
17 of the 21 blood testing panels we itemize marker by marker include Cortisol in their panels. This biomarker is widely available across major providers.
Related: YouBoost rates lifestyle and supplement interventions by evidence; HRV Zone tracks recovery trends.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed Sep 23, 2026 · First published Sep 30, 2025