What cortisol is
Cortisol is a glucocorticoid hormone produced by the adrenal cortex (zona fasciculata) in response to ACTH (adrenocorticotropic hormone) from the pituitary gland, which is itself stimulated by CRH (corticotropin-releasing hormone) from the hypothalamus. This three-tier cascade is called the HPA (hypothalamic-pituitary-adrenal) axis — the body's primary stress response system.
Cortisol has hundreds of functions: it regulates blood glucose (raises it by stimulating gluconeogenesis), modulates immune function, controls inflammation, affects mood and cognition, and coordinates the physiological stress response.
The diurnal pattern — why timing matters
Cortisol follows a precise circadian rhythm. It begins rising approximately 2 hours before waking, peaks 30–45 minutes after waking — the cortisol awakening response (CAR) — and then declines steadily throughout the day to its nadir around midnight. This rhythm drives morning alertness, immune activation, and metabolic signalling for the day ahead.
When this rhythm is disrupted — blunted in the morning or elevated at night — sleep, mood, immune function, and metabolic health all suffer. A flattened cortisol curve (low morning, still-elevated evening) is associated with burnout, metabolic syndrome, and increased mortality risk.
Morning serum vs salivary 4-point testing
Morning serum cortisol (at a lab, 7–9am): measures total cortisol including protein-bound fraction; good for a single snapshot of morning HPA axis function; convenient.
4-point salivary cortisol: measures free (active) cortisol at 4 time points — waking, noon, evening, bedtime. Provides the circadian curve, which is far more informative for assessing HPA axis health. Some labs in India offer salivary cortisol kits (DUTCH test equivalents). For any serious HPA axis investigation, salivary 4-point testing is superior.
Reference ranges vs optimal
| Morning Cortisol (mcg/dL) | Category | Pattern / Implication | Action |
|---|---|---|---|
| <5 mcg/dL | Very low — investigate | Possible adrenal insufficiency; prolonged steroid use history? | Physician evaluation; ACTH stimulation test; rule out Addison's |
| 5–10 mcg/dL | Low-normal (blunted) | Blunted CAR; HPA dysregulation; morning fatigue, coffee dependency | Sleep optimisation; ashwagandha; rhodiola rosea; stress management |
| 10–20 mcg/dL | Optimal | Healthy morning cortisol; good HPA function | Maintain; monitor stress and sleep quality |
| 20–25 mcg/dL | Borderline elevated | Stress burden or mild HPA hyperactivation | Ashwagandha KSM-66; sleep improvement; stress reduction; retest |
| >25 mcg/dL | Elevated — investigate | Chronic HPA hyperactivation; possible Cushing's syndrome if >30 | Repeat test; physician evaluation; 24-hour urine cortisol if Cushing's suspected |
What chronic high cortisol does
- Muscle catabolism — cortisol breaks down muscle protein for gluconeogenesis; impairs muscle protein synthesis; a primary driver of sarcopenia in chronically stressed individuals
- Bone loss — inhibits osteoblasts and promotes osteoclasts; prolonged elevation causes osteoporosis
- Central fat accumulation — cortisol promotes visceral fat deposition and activates lipoprotein lipase in abdominal adipocytes
- Insulin resistance — cortisol stimulates gluconeogenesis and inhibits glucose uptake, raising fasting blood glucose and insulin
- Immune suppression — useful acutely but chronic immune suppression increases infection risk
- Sleep disruption — elevated evening cortisol prevents the drop needed for sleep onset
- Testosterone and DHEA suppression — cortisol competes with testosterone at receptor level; high cortisol is directly anti-anabolic
Supplements for cortisol normalisation
- Ashwagandha KSM-66 — 300–600mg/day; multiple placebo-controlled RCTs showing 27–30% reduction in serum cortisol; the best-evidenced natural cortisol-lowering supplement
- Phosphatidylserine — 400–600mg/day; blunts cortisol response to exercise and psychological stress; specifically reduces post-exercise cortisol elevation
- Rhodiola rosea — standardised extract 200–400mg/day; adaptogen that improves stress resilience and reduces cortisol in chronic stress; especially useful for "burnout" phenotype
- Magnesium glycinate — 200–400mg/day; magnesium deficiency is associated with HPA axis hyperreactivity; correcting deficiency normalises cortisol response
- L-theanine — 200mg; attenuates cortisol and anxiety response acutely; pairs well with caffeine
Sleep is the single most powerful cortisol regulator. Consistent 7.5–9 hours of quality sleep — in darkness, in a cool room, at consistent timing — normalises the cortisol curve more than any supplement. Supplements are adjuncts to, not substitutes for, sleep and stress management.
How often to test
Annually as part of a hormonal panel if symptomatic (fatigue, stress, body composition issues). Always test morning cortisol at 7–9am fasting for a meaningful single-point reading. Consider 4-point salivary testing if HPA axis investigation is warranted.
Frequently asked questions
What is a normal morning cortisol level in India?
Lab normal is 6–23 mcg/dL. Optimal for longevity is 10–20 mcg/dL — a healthy morning cortisol peak. Below 5 mcg/dL requires physician evaluation for adrenal insufficiency. Above 25 mcg/dL chronically warrants investigation and lifestyle intervention.
Can I test cortisol at home?
Yes — salivary cortisol kits provide the most informative assessment through a 4-point test (waking, noon, evening, bedtime) that shows the circadian curve. More clinically useful than a single morning serum reading for assessing HPA axis health.
Which supplements lower cortisol?
Ashwagandha KSM-66 (300–600mg/day) has the strongest evidence — 27–30% cortisol reduction in RCTs. Phosphatidylserine, rhodiola rosea, and magnesium glycinate all have supporting evidence. Sleep remains the most powerful intervention.
What causes cortisol to be too low?
Low morning cortisol (below 5 mcg/dL) can indicate adrenal insufficiency (Addison's disease) or secondary causes. Prolonged corticosteroid use (prednisolone, etc.) is a common suppressor. Requires ACTH stimulation testing to evaluate adrenal reserve — physician evaluation is essential.