How to test for high cortisol: the tests clinicians use

If you want to know how to test for high cortisol, the answer is not a single blood draw at a random time. Doctors check for a long-term excess of cortisol, called Cushing’s syndrome, with a urine, saliva or dexamethasone test, and they usually do two of them.

That surprises many people who expected a simple “cortisol blood test”. This page explains which tests are used, what each one involves, where a blood cortisol does and doesn’t fit, and when to bring the question to a clinician. It is general information and not a way to read your own result.

Cortisol

One blood draw for one cortisol result. It can’t diagnose or rule out an adrenal condition by itself.

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A single blood cortisol is not a screening test for Cushing's syndrome. It gives a number to take to a clinician. If you take a steroid medicine, ask your prescriber before you change anything.

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What “high cortisol” can mean

Two different things get called high cortisol, and the tests differ.

• Cushing’s syndrome. NIDDK describes it as a disorder in which the body makes too much cortisol over a long period. The most common cause is long-term, high-dose use of glucocorticoid medicines, which are used for conditions such as asthma, rheumatoid arthritis and lupus, and are sometimes injected into a joint. Other causes are tumors of the pituitary gland, the adrenal gland or elsewhere.
• A high reading without Cushing’s syndrome. MedlinePlus says stress, pregnancy, exercise, hot and cold temperatures and some medicines, such as birth control pills, can change cortisol levels. NIDDK also describes pseudo-Cushing’s syndrome, where cortisol is high off and on in people with depression or anxiety, heavy alcohol use, diabetes with persistently high blood glucose, or obesity, without the long-term effects of Cushing’s syndrome.

The symptoms NIDDK lists for Cushing’s syndrome are weight gain, thin arms and legs, a round face, extra fat at the base of the neck, easy bruising, wide purple stretch marks and weak muscles. It adds that not everyone has them, which can make the condition hard to detect, and that in people with type 2 diabetes and persistently high blood glucose and high blood pressure, Cushing’s syndrome may be the cause. Having one of these signs doesn’t mean you have it. See high cortisol symptoms for the wider picture.

How to test for high cortisol: the screening tests

NIDDK says diagnosis starts with your medical history, a physical exam and lab tests. Your doctor may first ask whether you take glucocorticoids or have had injections, and rule that out before ordering lab tests. Then, because no one test is perfect, doctors usually do two of these:

Test	What you do	What it checks	Known limits
24-hour urinary free cortisol	Collect all urine for 24 hours in a container, kept in a refrigerator or cooler (MedlinePlus)	Cortisol made over a whole day	Needs a complete collection. Very high fluid intake and reduced kidney function can mislead it. Two collections are recommended because day-to-day variation is high. Less sensitive for mild cases.
Late-night salivary cortisol	Collect saliva at home late in the evening, ideally at usual bedtime, at least twice	Whether cortisol drops at night the way it normally does	Not suitable for night-shift workers or disturbed sleep. Smoking, chewing tobacco, licorice, blood in the mouth or steroid contamination can raise it.
Low-dose dexamethasone suppression test	Take dexamethasone around 11 p.m. and have blood drawn about 8 a.m. the next day (NIDDK)	Whether cortisol falls after the steroid, as it normally does	Pregnancy, some epilepsy medicines, birth control pills, kidney problems and other drug interactions can affect it.

The limits come from a 2026 review in the Journal of Clinical Endocrinology and Metabolism and a 2023 laboratory review. For saliva collection at home, MedlinePlus says to follow the kit exactly: no eating, drinking, brushing or flossing for 30 minutes before, and to hold the swab in your mouth for about 2 minutes. A late-night saliva test and the other two belong with a clinician, who chooses and interprets them. The saliva, urine and hair page compares the sample types.

One more point about saliva. A 2020 commentary in the Journal of the Endocrine Society says that in a study of 705 people with suspected Cushing’s syndrome, most of those with one or more elevated late-night saliva results did not have it, and that one elevated value had poor specificity. That is why clinicians repeat and combine tests instead of acting on one number.

Can a blood test show high cortisol?

A blood cortisol measures cortisol, so it can report a high number. The problem is what a single number means.

• Time of day. Cortisol is normally highest in the morning and lowest around midnight. A laboratory review says random specimens are of no use for assessing Cushing’s syndrome, and that samples must be timed or be part of a dynamic test. A review for general practitioners says using a random cortisol to screen for Cushing’s syndrome is unreliable and not recommended.
• Carrier proteins. Standard blood tests report total cortisol. About 90% of it is attached to a carrier protein called CBG. Oral estrogens and pregnancy raise CBG, which raises total cortisol on its own, apart from any change in the active, free part. Urine and saliva tests measure free cortisol and are not affected by this. See free and total cortisol.
• The question being asked. The Cushing’s tests are built around the late-night low point or a dexamethasone challenge, not around a morning or 4 p.m. sample. A blood cortisol does have a role inside the dexamethasone test, where the morning blood draw is the measurement.

So a blood cortisol you order yourself is a first look at one number. The seller’s own page for its single cortisol test says a single value is hard to interpret and that provocative (dynamic) testing is required to evaluate excess or low cortisol. Treat the result that way: as something to take to a clinician, along with your symptoms and a list of everything you take.

What happens after an unusual result

Don’t try to read it alone. MedlinePlus says a cortisol test alone can’t diagnose the cause of an abnormal level, and that you will usually have more tests. Possible next steps, all arranged by a clinician, include repeating a screening test, and a dexamethasone-CRH test, which NIDDK says helps tell Cushing’s syndrome from other causes of high cortisol. If Cushing’s syndrome is confirmed, further blood tests and imaging look for the source. Most of the work-up sits with a doctor, often an endocrinologist, and not with the lab menu.

Never stop or lower a steroid medicine on your own, even if you suspect it is raising your cortisol. NIDDK says that when long-term glucocorticoids are the cause, the doctor reduces the dose gradually. Stopping suddenly can bring on low cortisol, which is a medical problem of its own. Talk to the prescriber first.

When to see a clinician

Book an appointment if you have several of the signs above, if you take steroid medicines and have developed them, or if you have type 2 diabetes with persistently high blood glucose and high blood pressure and have been wondering about Cushing’s syndrome. Bring up your symptoms and what you take. A blood cortisol in the printed range doesn’t rule Cushing’s syndrome out, so if the signs continue, still raise them with a clinician. Adrenal fatigue is not a recognized diagnosis, and a 2024 paper in the Journal of the Endocrine Society says the saliva cortisol profiles sold for it have never been validated. See adrenal fatigue for what the evidence says.

Questions people ask

Is there a test for high cortisol?

Yes. The tests used to check for Cushing’s syndrome are the 24-hour urine collection, the late-night saliva test and the low-dose dexamethasone suppression test. A blood cortisol can show a level at one moment, but on its own it can’t confirm or rule out the condition.

How do I know if I have high cortisol?

You can’t tell from symptoms alone. NIDDK says symptoms vary and that not everyone with Cushing’s syndrome has them. Many of the signs, such as weight gain, can have other causes. The only way to know is testing arranged with a clinician.

Do I need a doctor to order these tests?

Doctors arrange the tests NIDDK describes. MedlinePlus says many at-home test kits are available without a prescription, including self-collection kits where you take a sample at home and mail it to a lab. It advises using only tests the FDA has approved or authorized, following the directions closely, and following up with a provider whatever the result. A result from a home kit is not a diagnosis. For more on the practical side, see cortisol test names and our cortisol test guide.