Cortisol Levels: Normal Ranges, Testing & What Results Mean
Medically reviewed by Medical Advisory Board Last reviewed 2026-05-13
Understanding your cortisol numbers — serum, saliva, and urine testing explained
Cortisol levels vary dramatically throughout the day (diurnal variation), by testing method (serum, saliva, urine), and by individual stress state. Understanding how to interpret your cortisol results — and when each test type is appropriate — is essential for accurate diagnosis.
Cortisol is the body's primary stress hormone, produced by the adrenal cortex under regulation of the HPA (hypothalamic-pituitary-adrenal) axis. A single cortisol measurement is difficult to interpret without context — levels fluctuate 5-10x throughout the day, are affected by acute stress, medications, sleep timing, and testing method.
Three testing methods are used clinically: serum (blood) cortisol, salivary cortisol, and 24-hour urinary free cortisol (UFC). Each has distinct advantages and limitations, and they measure different fractions of cortisol (total vs. free vs. metabolized). The Endocrine Society recommends specific tests for specific clinical questions.
High Cortisol Levels: Symptoms, Causes, and Next Steps
High cortisol levels can mean very different things depending on timing and test type. A high morning cortisol after poor sleep or acute stress is not the same as persistently elevated late-night salivary cortisol, which suggests loss of normal diurnal rhythm. The clinical question is whether cortisol is high once, high throughout the day, or failing to fall at night.
| Pattern | Common Clues | Best Next Test |
|---|---|---|
| High morning cortisol | Acute stress, poor sleep, pain, caffeine, intense exercise | Repeat AM serum cortisol under controlled conditions |
| High evening cortisol | Insomnia, wired-but-tired feeling, night waking | 4-point salivary cortisol curve |
| Very high 24-hour cortisol | Easy bruising, purple striae, proximal weakness, rapid central weight gain | 24-hour urinary free cortisol and late-night salivary cortisol |
| High cortisol with high glucose/insulin | Belly fat, cravings, energy crashes | Fasting insulin, A1C, lipids, waist circumference |
For symptom-first triage, compare this page with high cortisol symptoms, cortisol imbalance, and how to lower cortisol naturally.
Cortisol Reference Ranges by Test Type
| Test | Time | Reference Range | Optimal Range | Notes |
|---|---|---|---|---|
| Serum cortisol | AM (7-9 AM) | 6.2–19.4 μg/dL | 10–18 μg/dL | Draw before 9 AM after overnight rest |
| Serum cortisol | PM (4 PM) | 2.3–11.9 μg/dL | 3–8 μg/dL | Should be ~50% of AM value |
| Salivary cortisol | Morning (waking) | 0.15–0.70 μg/dL | 0.25–0.60 μg/dL | Collect within 30 min of waking |
| Salivary cortisol | Night (11 PM) | <0.09 μg/dL | <0.04 μg/dL | Key screening for Cushing's |
| 24-hr urinary free cortisol | Full day | 4–50 μg/24h | 10–40 μg/24h | Best for suspected Cushing's syndrome |
Note: Reference ranges vary by lab. Always compare to the specific lab's reference range on your report.
When to Use Each Test
AM serum cortisol: Best for screening for adrenal insufficiency (low cortisol). A morning cortisol below 3 μg/dL is strongly suggestive of adrenal insufficiency; above 18 μg/dL effectively rules it out. Values between 3-18 require further testing (ACTH stimulation test).
4-point salivary cortisol: Best for evaluating diurnal rhythm and functional cortisol dysregulation (stress-related). Provides the most complete picture of your cortisol pattern throughout the day. Preferred for evaluating fatigue, insomnia, and suspected HPA axis dysfunction. Advantages: non-invasive, collected at home, measures free (bioactive) cortisol.
Late-night salivary cortisol: Best screening test for Cushing's syndrome. Cortisol should be at its lowest at midnight; persistent elevation indicates loss of diurnal rhythm.
24-hour urinary free cortisol: Measures total daily cortisol output. The Endocrine Society recommends this as a first-line screening test for Cushing's syndrome. Values >3x upper limit of normal are highly diagnostic.
ACTH stimulation test: Definitive test for adrenal insufficiency. IV ACTH is administered, and cortisol response is measured at 30 and 60 minutes. Normal response: cortisol >18 μg/dL.
Factors That Affect Cortisol Results
- Time of day: Morning levels are 5-10x higher than midnight levels. Always note collection time.
- Acute stress: Blood draws, anxiety, and pain acutely elevate cortisol. A stressful blood draw may produce falsely elevated results.
- Medications: Oral contraceptives increase cortisol-binding globulin (CBG), raising total serum cortisol by 50-100% without increasing free cortisol. Salivary cortisol is unaffected. Exogenous glucocorticoids (even topical/inhaled) suppress endogenous cortisol.
- Sleep timing: Night-shift workers have shifted cortisol rhythms. Testing should align with their sleep-wake pattern, not clock time.
- Exercise: Intense exercise within 2-3 hours of testing elevates cortisol.
- Alcohol: Heavy alcohol use increases cortisol (pseudo-Cushing's syndrome).
Frequently Asked Questions
What is a normal cortisol level in the morning?
Morning serum cortisol (drawn at 7-9 AM) normally ranges from 6.2 to 19.4 μg/dL, with optimal levels between 10-18 μg/dL. Morning salivary cortisol (within 30 minutes of waking) is typically 0.15-0.70 μg/dL. Levels below 3 μg/dL (serum) suggest adrenal insufficiency; levels below 10 μg/dL may indicate suboptimal adrenal function.
Is salivary cortisol testing accurate?
Yes. Salivary cortisol measures free (unbound, bioactive) cortisol and correlates well with serum free cortisol. It has excellent sensitivity and specificity for both Cushing's syndrome (late-night salivary cortisol) and adrenal insufficiency (morning salivary cortisol). Advantages over serum: non-invasive, no stress from blood draw, can be collected at home at multiple time points, and not affected by oral contraceptives' elevation of CBG.
Can I lower my cortisol levels too much?
Yes. Cortisol is essential for life — it regulates blood sugar, blood pressure, immune function, and inflammation. Very low cortisol (adrenal crisis) is a medical emergency. When using cortisol-lowering strategies (adaptogens, stress management), the goal is to normalize the diurnal rhythm, not eliminate cortisol. If you develop worsening fatigue, lightheadedness, or salt cravings while trying to lower cortisol, your levels may already be low — retest before continuing.
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