Cortisol results —
what high or low
actually means.
Your cortisol result is outside the range and you're not sure if you should be worried. Cortisol is one of the most misunderstood lab values — because timing and context matter as much as the number itself.
Dr. Emma Walsh, MD, MPH
Preventive Medicine, Thyroid Disorders ·
The essentials — before you read the full guide below.
Timing is everything
Cortisol peaks 30–45 minutes after waking (6–23 mcg/dL), falls through the day, and is lowest at midnight. The same number at 8am and 8pm means completely different things.
Morning reference range
Morning cortisol: 6–23 mcg/dL. Afternoon: 2–11 mcg/dL. Midnight: <2 mcg/dL. Always check when your blood was drawn before interpreting.
"Adrenal fatigue" isn't a real diagnosis
"Adrenal fatigue" is not a recognised medical diagnosis. True adrenal insufficiency (Addison's disease) is rare and serious — confirmed by ACTH stimulation testing.
Stress raises cortisol temporarily
Acute illness, anxiety, surgical procedures, and even the blood draw itself can temporarily elevate cortisol. Single elevated values are often not clinically significant.
Reference Ranges
What does your number
actually mean?
Use the interactive slider below, or read the range cards for a full clinical breakdown.
Cortisol (Stress Hormone) Reference Ranges
mcg/dL (morning sample)Enter your result
Drag to see what your Cortisol (Stress Hormone) means
The Science
The cortisol rhythm — why one number isn't enough
Cortisol follows one of the most dramatic diurnal rhythms in human biology. A single random cortisol is often meaningless without knowing what time it was drawn. Understanding the rhythm explains why context determines clinical significance.
Cortisol surges 30–45 mins after waking
The Cortisol Awakening Response (CAR) — a sharp rise in the first 30–45 minutes after waking — is the body's primary metabolic "start signal." This is why morning samples are most diagnostically informative.
The HPA axis controls cortisol output
The Hypothalamic-Pituitary-Adrenal (HPA) axis controls cortisol: hypothalamus releases CRH → pituitary releases ACTH → adrenals produce cortisol. Disruption at any level causes dysfunction.
Chronic stress flattens the rhythm, not the level
Burnout and chronic stress flatten the diurnal curve — morning peaks diminish, evening stays high. A single cortisol can be "normal" while the rhythm is completely disrupted.
When to Test
Signs your doctor will
order this test
These are the most common reasons a Cortisol (Stress Hormone) test is requested — from symptoms to routine screening.
Profound fatigue & weakness (Low)
Adrenal insufficiency causes extreme fatigue, muscle weakness, weight loss, low blood pressure, and salt cravings.
Addison's signsSkin hyperpigmentation (Low cortisol)
In primary adrenal insufficiency, elevated ACTH stimulates melanin production — causing bronzing of the skin in skin creases.
Addison's signCentral weight gain & round face (High)
Cushing's syndrome causes fat redistribution to the abdomen, back ("buffalo hump"), and face ("moon face").
Cushing's signsPurple stretch marks (High cortisol)
Wide, purple striae on the abdomen, thighs, or breasts are a specific sign of Cushing's syndrome.
Cushing's signLong-term steroid use
Chronic use of oral, topical, or inhaled corticosteroids suppresses natural cortisol production — the most common cause of Cushing's.
Drug-induced riskHypoglycaemia episodes
Low cortisol impairs the body's ability to maintain blood glucose, causing hypoglycaemic episodes — especially during fasting.
Metabolic signTesting Schedule
How often should
you get tested?
Frequency depends on your current health status and your doctor's guidance.
Suspected adrenal insufficiency
A random cortisol is combined with an ACTH stimulation test for definitive diagnosis — single values alone are insufficient.
Cushing's investigation
24-hour urine free cortisol, late-night salivary cortisol (11pm), and morning serum cortisol together provide the most accurate assessment.
Monitoring adrenal disorders
Patients with confirmed adrenal insufficiency or Cushing's are monitored at intervals set by their endocrinologist.
Chronic stress or fatigue
Routine cortisol for non-specific fatigue is not clinically recommended. Consider 4-point salivary cortisol if rhythm dysregulation is suspected.
If Your Result Is Abnormal
Managing cortisol dysfunction
True adrenal disorders require medical treatment. For cortisol rhythm dysregulation from lifestyle stress, these evidence-based interventions help normalise the HPA axis.
Consistent sleep schedule
Fixed wake times (even weekends) stabilise the Cortisol Awakening Response. Irregular sleep is one of the strongest disruptors of HPA rhythm.
Restores diurnal rhythmMindfulness & breathwork
Slow diaphragmatic breathing activates the parasympathetic nervous system, acutely lowering cortisol within 10 minutes. Daily practice lowers baseline.
Proven cortisol reductionModerate exercise
Moderate intensity exercise (60–70% max HR, 30–45 min) reduces chronic cortisol. Very high-intensity training without adequate recovery can chronically elevate cortisol.
Lowers chronic cortisolAshwagandha (KSM-66)
KSM-66 ashwagandha extract (600mg/day for 60 days) has the strongest published evidence for reducing serum cortisol in chronically stressed adults — two RCTs showing 15–28% reduction.
−15 to −28% cortisol