---
title: "How to Test Cortisol Levels: Blood, Saliva or Urine, When to Draw, and How to Read the Result"
type: guide
url: "https://www.test-well.com/guides/how-to-test-cortisol-levels"
date_published: 2026-10-19
reviewed_at: 2026-10-19
---

# How to Test Cortisol Levels: Blood, Saliva or Urine, When to Draw, and How to Read the Result

*Cortisol changes by the hour, so the right test depends on the question — too little, too much, or a rhythm that is off. Here is how each test works, when to collect it, what skews it, and what the numbers mean.*

> The standard first test is a morning blood cortisol drawn between 7 and 9 AM, when the level peaks — it screens for low cortisol and gives a baseline. A suspected high cortisol (Cushing syndrome) is screened differently: with a late-night saliva sample, a 24-hour urine collection or a dexamethasone suppression test, because a single daytime blood value cannot show the lost rhythm. No fasting is needed; oral estrogen, steroid medications and high-dose biotin are the common things that distort the result.

## Recommended tests

| Recommended | Type | Price | Why |
| --- | --- | --- | --- |
| [Cortisol (AM)](https://www.test-well.com/tests/cortisol-am) | Test | $26.99 | The 7–9 AM blood cortisol — the first-line screen and baseline |
| [Cortisol, PM](https://www.test-well.com/tests/cortisol-pm) | Test | $34.99 | A 3–5 PM draw added to the morning value to see the daily fall |
| [Sleep Health Panel](https://www.test-well.com/tests/sleep-health-panel) | Panel (8 tests) | $129.99 | AM and PM cortisol with thyroid, iron, vitamin D, magnesium and A1c for poor sleep |

All prices are cash-pay plus one $6 lab processing fee per order; physician authorization is included.

## Why timing is the whole test

Cortisol follows a daily rhythm: it peaks in the half hour after waking, falls steeply through the morning, drifts lower through the afternoon and reaches its lowest point around midnight. A value that is normal at 8 AM would be alarming at 11 PM, and a value that is normal at 4 PM would be worryingly low at 8 AM. Laboratories publish separate reference ranges for morning and afternoon draws for exactly this reason, and a cortisol result without a collection time is close to uninterpretable.

The rhythm also decides which test answers which question. When the worry is *too little* cortisol (adrenal insufficiency), the peak is the informative moment: a morning value that is clearly normal effectively rules it out. When the worry is *too much* cortisol (Cushing syndrome), the informative moment is the trough: the disease shows up as a midnight level that fails to fall, which no single daytime blood draw can detect. That is why the screening tests for high cortisol are late-night saliva, 24-hour urine and the dexamethasone suppression test, not a morning blood test.

## Which cortisol test do you need?

| Question | Test | When to collect | What it shows |
| --- | --- | --- | --- |
| Fatigue, dizziness on standing, low blood pressure, salt craving, weight loss — could cortisol be low? | Morning blood (serum) cortisol | 7–9 AM, ideally within an hour of waking | A clearly normal morning value makes adrenal insufficiency unlikely; a low value is followed by an ACTH stimulation test |
| A baseline, or symptoms that do not fit a pattern | Morning blood cortisol, often with a PM draw | 7–9 AM and 3–5 PM | Whether the level peaks in the morning and falls by afternoon as it should |
| Weight gain in the face and trunk, purple stretch marks, easy bruising, high blood pressure or blood sugar — could cortisol be high? | Late-night salivary cortisol (two nights), 24-hour urine free cortisol (two collections), or a 1 mg overnight dexamethasone suppression test | Saliva at 11 PM–midnight; urine over a full 24 hours; dexamethasone at 11 PM with blood at 8 AM | Loss of the midnight trough, total daily output, or failure to suppress — the three accepted screens for Cushing syndrome |
| Sleep disruption, stress, "burnout" | Morning and afternoon blood cortisol | 7–9 AM and 3–5 PM | A flattened or inverted curve; useful context, not a diagnosis — "adrenal fatigue" is not a recognised condition |
| Monitoring steroid medication, or after stopping long-term steroids | Morning blood cortisol | 7–9 AM, before the day's dose | Whether the adrenal glands have recovered their own production |

Through TestWell you can order the [morning blood cortisol](https://www.test-well.com/tests/cortisol-am) and the [PM cortisol](https://www.test-well.com/tests/cortisol-pm) without a referral; the late-night saliva, 24-hour urine and dexamethasone tests are arranged by a clinician because they need specific collection kits or a prescribed dose.

## How to prepare for a cortisol blood test

**Book the draw for 7–9 AM** and keep your usual sleep schedule the night before; shift workers should tell the lab and their clinician when they woke, because the reference range assumes a conventional night's sleep. No fasting is needed. Avoid vigorous exercise that morning and arrive a few minutes early so you are seated calmly before the draw — exertion and acute stress both raise cortisol for a short time.

Medications matter more than food. **Oral estrogen** (combined contraceptives, menopausal hormone therapy) raises cortisol-binding globulin and therefore total cortisol, often into or above the upper range, without changing the active hormone; clinicians either account for it or test after a pause. **Steroid medications** cut both ways: prednisone and some other glucocorticoids cross-react in the cortisol assay and read as cortisol, while any steroid taken for weeks — tablets, inhalers, joint injections, potent skin creams — suppresses your own production and lowers the result. Tell your clinician about every steroid, including inhaled and topical ones. **High-dose biotin** supplements can interfere with the immunoassays most labs use; stop them two days before. Severe illness, major surgery and pregnancy raise cortisol physiologically.

## How to read a cortisol result

Morning serum cortisol reference ranges run roughly 6–23 mcg/dL (165–635 nmol/L), with the lab's own range printed on the report; afternoon values are expected to be about half the morning value. The interpretation is asymmetric. For *low* cortisol, a morning value under about 3 mcg/dL strongly suggests adrenal insufficiency and one above about 15–18 largely excludes it; the band between is indeterminate and is resolved with an ACTH (cosyntropin) stimulation test, which measures how much the adrenal glands can produce when told to. For *high* cortisol, a raised morning value on its own proves little — stress, estrogen, obesity, depression, alcohol and poorly controlled diabetes all raise it — which is why Cushing syndrome is screened with the late-night, urine or suppression tests and confirmed with at least two abnormal results before imaging is considered.

What the number cannot do is diagnose "adrenal fatigue". The concept — that chronic stress exhausts the adrenal glands and produces low-normal cortisol — has been tested repeatedly and is not supported; the Endocrine Society and other bodies do not recognise it. Fatigue with a normal cortisol usually has a different, findable cause: thyroid, iron, B12, vitamin D, blood sugar, sleep apnoea or depression, which is why the fatigue and sleep panels test cortisol alongside those rather than alone.

## When to see a clinician rather than retest

Same-day medical care is needed for the picture of an adrenal crisis — severe weakness, vomiting, confusion, low blood pressure or fainting, especially in someone on long-term steroids or with a known adrenal or pituitary condition. Otherwise, a morning cortisol below the lab's range, or any high-cortisol screening result, is a reason to book a visit rather than to order the test again: the next steps (ACTH stimulation, a second screening method, imaging) are sequenced by a clinician. A normal morning cortisol with persistent symptoms is a reason to look elsewhere, and the result is still useful — it closes a door.

## Frequently asked questions

### How do you test cortisol levels?

With a blood draw timed to the hormone's rhythm — 7–9 AM for the standard screen, sometimes with a 3–5 PM draw — or, when high cortisol is suspected, with a late-night saliva sample, a 24-hour urine collection or an overnight dexamethasone suppression test. The blood tests can be ordered online and drawn at a Quest or Labcorp patient service center; the others are arranged through a clinician.

### What time of day should a cortisol blood test be done?

Between 7 and 9 AM, ideally within an hour of waking, for the morning test; between 3 and 5 PM for the afternoon test. Reference ranges are specific to the collection window, so note the time on your paperwork and keep your usual sleep schedule the night before.

### Do you need to fast for a cortisol test?

No. Food does not meaningfully affect cortisol. What does: strenuous exercise and acute stress right before the draw (both raise it briefly), oral estrogen, steroid medications in any form, high-dose biotin, severe illness and pregnancy.

### What is a normal cortisol level?

Morning serum cortisol is typically about 6–23 mcg/dL (165–635 nmol/L) and afternoon values roughly half that, with the performing lab's range printed on your report. Late-night saliva is normally very low; a value above the lab's cut-off on two nights is a positive screen for Cushing syndrome.

### Can a blood test detect Cushing syndrome?

Not a single daytime blood test. Cushing syndrome shows as a lost midnight trough and excess total output, so the accepted screens are late-night salivary cortisol, 24-hour urine free cortisol and the 1 mg overnight dexamethasone suppression test — the last of which is a blood test, drawn at 8 AM after a tablet the night before. A morning cortisol alone can be normal in Cushing syndrome.

### Is adrenal fatigue real, and can a cortisol test diagnose it?

Adrenal fatigue is not a recognised medical diagnosis, and no cortisol pattern defines it. Adrenal insufficiency — a real and serious condition — is diagnosed with a morning cortisol and an ACTH stimulation test. Fatigue with a normal cortisol usually has another findable cause: thyroid, iron, B12, vitamin D, blood sugar, sleep or mood.

### How much does a cortisol test cost?

The morning blood cortisol is one of the less expensive hormone tests; the labs' own consumer sites list it at $79–$89 and clinic visits add a visit fee. The full cost breakdown by route, with and without insurance, is in our cortisol test cost guide.

## Sources

- [Endocrine Society — The Diagnosis of Cushing's Syndrome: Clinical Practice Guideline (Nieman et al., 2008)](https://academic.oup.com/jcem/article/93/5/1526/2598096)
- [Endocrine Society — Diagnosis and Treatment of Primary Adrenal Insufficiency: Clinical Practice Guideline (Bornstein et al., 2016)](https://academic.oup.com/jcem/article/101/2/364/2810222)
- [MedlinePlus (NIH) — Cortisol Test](https://medlineplus.gov/lab-tests/cortisol-test/)
- [NIDDK — Adrenal Insufficiency & Addison's Disease](https://www.niddk.nih.gov/health-information/endocrine-diseases/adrenal-insufficiency-addisons-disease)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-10-19. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md

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Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.