How to Test Cortisol Levels: Which Test to Take, When, and Where

A plain map of the five ways to measure cortisol, which question each sample answers, when to collect it, and which ones you can collect at home.

Published

September 28, 2026

Read time

9 min read

Medically reviewed by

Rhonda Collins, FNP-C

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Quick Summary

To test your cortisol, first decide what question you are asking, because cortisol changes through the day and the time of collection shapes what a result means. A morning blood test looks at cortisol near its daily high. A late-night saliva test or a 24-hour urine test looks for cortisol that stays too high. Source: Labcorp.

You can collect some cortisol tests yourself at home. Mito’s saliva and 24-hour urine tests are collected at home and analyzed by Quest Diagnostics. Blood tests are drawn at a lab, and some of them can be drawn at home by a phlebotomist where Mito offers home draw.

Which cortisol test should you take?

Match the sample to the question. Each option below links to Mito’s exact product page, which has current pricing, availability, and collection instructions.

If you want one general starting point, the Cortisol Blood Test is the standard serum cortisol test. Mito offers it through Quest Diagnostics, Labcorp, and BioReference, and it is eligible for home draw where that service is available.

Why does the time of day matter for a cortisol test?

Serum cortisol normally follows a daily rhythm. It is usually highest early in the morning, then declines through the day to an evening level about half the morning level. Because of that rhythm, a lab reads a cortisol result against the time the sample was collected. Source: Labcorp.

Cortisol production normally drops just after you fall asleep. In Cushing’s syndrome, that night-time drop is often lost, which is why late-night samples carry information that a morning sample does not. Source: NIDDK.

This is also why a cortisol result from the wrong time of day can mislead. A normal morning level and a normal late-night level are very different numbers. The normal cortisol levels guide explains how labs set ranges by time of day and sample type.

What does each cortisol test show, and what can it miss?

Morning blood cortisol

A morning serum cortisol test measures total cortisol near the daily peak. BioReference asks for the sample ideally between 6 a.m. and 8 a.m. Source: BioReference. A low morning level is one reason a clinician looks further at adrenal insufficiency. The Endocrine Society lists morning cortisol, with ACTH, as an initial screening step when a stimulation test is not possible first. Source: Endocrine Society guideline, 2016.

A single morning value cannot show whether cortisol falls normally later in the day, and it cannot confirm a diagnosis on its own.

Evening blood cortisol

An evening serum cortisol test measures total cortisol in a late-afternoon sample. BioReference asks for it ideally around 4 p.m. Source: BioReference. Paired with a morning sample, it shows whether cortisol has fallen across the day. Labcorp describes drawing at 8 a.m. and 4 p.m. to evaluate this daily variation. Source: Labcorp.

On its own, an afternoon level says little, because it is read against the expected drop from the morning.

Multiple-specimen blood cortisol

The Cortisol, 3 Specimens test measures total cortisol in three separate serum samples on one order, so the lab reports how the level differs between them. Source: Quest Diagnostics. It is useful when timed comparisons matter. It still measures blood cortisol only at the moments each sample was drawn.

Late-night saliva cortisol

Late-night salivary cortisol measures cortisol in saliva collected at night, when it is normally at its lowest. Quest describes it as useful in screening for Cushing’s syndrome, because people with Cushing’s syndrome often lose the late-night low. Quest measures it by mass spectrometry. Source: Quest Diagnostics.

It has limits. Quest notes it should not be used for screening in people without normal day and night cycles, and that it has low sensitivity for adrenal tumors. Conditions such as obesity, psychiatric disorders, alcohol use disorder, and polycystic ovary syndrome can also raise the result. Source: Quest Diagnostics.

24-hour urine free cortisol

A 24-hour urine free cortisol test measures the unbound cortisol in all the urine you pass over one full day. Because it pools a whole day, it averages out the daily rhythm and does not depend on the binding proteins that affect blood tests. Quest calls it one of the preferred tests for screening for Cushing’s syndrome. Source: Quest Diagnostics.

It is not recommended for screening in people with impaired kidney function or who pass unusually large volumes of urine. Source: Quest Diagnostics.

Can you test cortisol at home?

Yes, for saliva and urine. Mito’s two home-collected cortisol tests are:

• Cortisol, Saliva Test: you collect saliva at home at the time your instructions specify, usually late at night.
• Cortisol, Free, 24-Hour Urine Test: you collect all of your urine at home over one full day.

Both are lab tests, not instant readers: Quest Diagnostics analyzes the samples. Mito offers these two tests through Quest only, so availability depends on your state. The product page shows current availability.

Blood cortisol needs a blood draw. The Cortisol Blood Test, Cortisol, AM Blood Test, and Cortisol, P.M. Blood Test can be drawn at a Quest, Labcorp, or BioReference lab, or at home by a phlebotomist where Mito offers home draw. The Cortisol, 3 Specimens Blood Test is a lab visit only.

Are home cortisol tests accurate?

Mito’s home-collected saliva and urine samples are analyzed by Quest Diagnostics using mass spectrometry, a laboratory method. Source: Quest Diagnostics, saliva; Quest Diagnostics, urine. Collecting at home does not change the lab method. What decides whether the result is useful is whether the sample was collected the right way at the right time. The common problems are:

• Wrong timing. A saliva sample collected at the wrong hour is read against the wrong expectation.
• An incomplete 24-hour collection. The urine test depends on collecting all urine for the full day. Source: MedlinePlus.
• An irregular sleep schedule. Late-night saliva testing assumes normal day and night cycles. Source: Quest Diagnostics.

No single cortisol test is perfect. NIDDK notes that doctors usually use two different tests to confirm Cushing’s syndrome, and the Endocrine Society recommends a second test after an abnormal first result. Source: NIDDK; Endocrine Society guideline, 2008.

How should you prepare for a cortisol test?

Several things besides a hormone disorder can change a cortisol result. Knowing them helps the result be read correctly.

• Steroid medicines. Prednisone, prednisolone, and methylprednisolone can make a blood cortisol result read falsely high. Source: Labcorp. The Endocrine Society also asks that outside glucocorticoid use be excluded before testing for Cushing’s syndrome. Source: Endocrine Society guideline, 2008.
• Estrogen-containing medicines and pregnancy. Birth control pills, estrogen therapy, and pregnancy raise blood cortisol concentrations. Source: Labcorp.
• Biotin. High-dose biotin supplements can interfere with some blood cortisol assays. Labcorp asks that biotin be stopped at least 72 hours before collection. Source: Labcorp.
• Stress and exercise. Both can raise cortisol, and severe stress can raise a blood result. Source: MedlinePlus; Labcorp.
• Sleep and shift work. Timed tests assume a normal sleep and wake schedule, so night shifts or disrupted sleep make a late-night saliva result hard to read. Source: Quest Diagnostics.
• Sample handling. Collect at the stated time, record that time, and follow the storage and return instructions that come with your test.

List every medicine and supplement you take when you order, so the result can be interpreted in context. MedlinePlus advises against stopping a prescribed medicine for the test without your provider’s approval. Source: MedlinePlus.

How is a cortisol disorder confirmed?

A clinician confirms or rules out a cortisol disorder with further testing, such as a dexamethasone suppression test or an ACTH stimulation test. Source: NIDDK; NIDDK.

What should you do with your cortisol result?

Read the result against the reference range and collection time printed on your lab report, not a generic number. Ranges differ by lab, sample type, and time of day. The normal cortisol levels guide explains those differences.

A cortisol result is not a diagnosis by itself. High levels can point toward Cushing’s syndrome and low levels toward adrenal insufficiency, but results need to be interpreted with symptoms and other tests. Source: MedlinePlus. The symptoms of high cortisol and symptoms of low cortisol pages describe what each pattern can look like.

If your result is outside the range, review it with a clinician, who can decide whether a second test is needed. For background on the hormone itself, see the cortisol biomarker page. If your level is low and you want to understand lifestyle factors, see raising cortisol naturally.

Test This with Mito

Start with the Cortisol Blood Test for a standard serum cortisol, or choose the exact test from the table above. Each product page has current pricing, lab options, and availability. For a side-by-side look at what cortisol tests cost, see the cortisol test cost guide.

Key Takeaways

• Cortisol follows a daily rhythm, so the collection time decides what a result can show.
• Morning and evening blood tests measure cortisol at single points in the day.
• Late-night saliva and 24-hour urine look for cortisol that stays too high, and both are collected at home.
• Steroid and estrogen-containing medicines, biotin, stress, and irregular sleep can all change a result.

Medical Disclaimer

This guide provides general education, not personal medical advice, diagnosis, or a treatment plan.

References

1. MedlinePlus: Cortisol Test.
2. NIDDK: Cushing’s Syndrome.
3. NIDDK: Diagnosis of Adrenal Insufficiency and Addison’s Disease.
4. Nieman LK, et al. The diagnosis of Cushing’s syndrome: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2008.
5. Bornstein SR, et al. Diagnosis and Treatment of Primary Adrenal Insufficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016.
6. Labcorp: Cortisol (004051).
7. Quest Diagnostics: Cortisol, LC/MS, Saliva (19897).
8. Quest Diagnostics: Cortisol, Free, 24-Hour Urine (14534).
9. Quest Diagnostics: Cortisol, 3 Specimens (7303).
10. BioReference: Cortisol, AM (0066-1) and Cortisol, PM (0067-9).