What Is a Cortisol Test?

A cortisol test measures the level of cortisol in your blood, urine or saliva. Cortisol is a hormone that's important throughout the body for maintaining blood pressure, blood sugar, and metabolism, as well as responding to infections and stress. Your doctor might order a cortisol test if they see symptoms that suggest your levels are either too high or too low.

A cortisol test can diagnose a number of problems in your pituitary or adrenal glands. (Photo credit: Jarun011/Dreamstime)

Cortisol is made by your adrenal glands, which are two small glands that sit on top of your kidneys. It helps you respond to stress and plays a key role in other functions, including how your body breaks down carbohydrates, lipids, and proteins. Cortisol also suppresses bodily inflammation and helps control your sleep-wake cycles.

Cortisol normally changes throughout the day. It's highest in the early morning and lowest around midnight. (If you happen to work at night and sleep during the day, the pattern will be reversed.) What's considered a normal cortisol range depends on the person, time of day, and the lab doing the testing. Typically, the normal cortisol ranges for an adult getting a blood test are:

6 a.m. to 8 a.m.: 10-20 micrograms per deciliter (mcg/dL)

Around 4 p.m.: 3-10 mcg/dL

The normal ranges are slightly different for children and the elderly.

For the urine test, the normal cortisol reference range is 10-55 micrograms per day (mcg/day) for adults.

For the saliva test, the normal range for adults is:

10.2-27.3 nanograms per milliliter(ng/mL) in the morning

2.2-4.1 ng/mL at night

Symptoms of high cortisol levels

Signs of a high level of cortisol include:

Rapid weight gain

Round face

Fatty hump at the base of the neck and/or between the shoulders

High blood pressure

High blood sugar

Skin changes (bruises and purple stretch marks)

Muscle weakness

Weak bones

Feeling anxious or depressed

Irregular periods in women

The symptoms depend on how elevated your cortisol levels are. Very high levels of cortisol are usually a sign of a condition called Cushing's syndrome. Cushing's syndrome may be caused by:

Symptoms of low cortisol levels

These include:

Fatigue

Dizziness

Weight loss

Low blood pressure

Low levels of cortisol may be due to:

Along with checking for Cushing's syndrome and Addison's disease, the tests can screen for other diseases that affect your pituitary and adrenal glands. The test might also show whether you're under severe stress.

Although the cortisol test is mostly done by drawing your blood, you can also check your cortisol levels via urine or saliva samples.

If the doctor orders the test, the sample might be taken in the doctor's office or at a lab. If you're doing this test on your own, you may order an at-home kit or go to a lab.

Since stress can raise cortisol levels, you may be asked to rest for a day before doing the test or to stop using certain medications while conducting the test.

At-home cortisol tests

You can test your cortisol levels at home. These cortisol tests, sometimes called at-home stress and sleep panels, involve buying a kit online or from a drugstore. You can use a blood, urine, or saliva sample depending on the type of test you buy. The test will include instructions on how to collect your sample. Once you've collected it, mail the sample back to the lab from which you bought the kit. They'll give you the results usually via an online account.

Some labs also provide a service where you can visit their location, have the sample taken by a lab tech, and then check the results online. This is often cheaper than using an at-home kit.

For the most accurate results, see your doctor to have the test done. They might want to compare the results against other tests.

Cortisol test price

As you'd expect, prices vary a lot depending on the type of test, lab used, and what your insurance will cover.

A blood test from one of the national lab chains will cost you around $72 provided you go to the lab to have the sample drawn. The at-home version will cost you about $130.

At-home cortisol tests in general can cost about $50-$400. Urine and saliva tests tend to be pricier than blood tests, but many of the higher-priced tests check more than just your cortisol level. At-home tests are not usually covered by insurance, but you might be able to use FSA or HSA funds.

Costs for cortisol tests covered by insurance will be similarly all over the map. For instance, one hospital estimated a charge of $157 for cash payments. However, if you use insurance, the price drops to $100, which would be covered by your insurance company assuming you've met your deductible and don't have a copay.

This test is sometimes called a serum cortisol test. Often, it's done twice on the same day -- once in the morning, and again later in the afternoon, around 4 p.m. That’s because cortisol levels change a lot throughout the day.

The test itself is simple. A nurse or lab technician will use a needle to take a blood sample from a vein in your arm.

Your results will show the level of cortisol in your blood at the time of the test. Your doctor will tell you if yours falls in the normal range.

If your level is too high, your doctor might follow up with other tests (urine or saliva) to make sure the results aren’t due to stress or a medication that acts like cortisol in your body.

Studies show that the saliva test is about 90% accurate in diagnosing Cushing's syndrome.

Your doctor will give you a kit and tell you what time to do the collection. Most likely you’ll do it at night before you go to bed. That’s because cortisol levels tend to be lowest between 11 p.m. and midnight. A high cortisol level near midnight can signal a disorder.

The kit should come with a swab and a tube for storage as well as instructions. Usually, you'll be told not to eat, drink, or brush your teeth for 30 minutes before the test. Then you'll roll the swab in your mouth for 2 minutes to collect the spit, put the swab back in the tube, and then take it back to the lab.

Cortisol Urine Test

Your doctor might order this to test what’s called "free" cortisol. This means the cortisol isn’t bound to a protein like the kind blood tests measure. If your doctor prescribes a urine test, you’ll need to provide a 24-hour sample.

Your doctor or lab tech will give you instructions on when to start the test and how to collect and store the urine sample. They'll also give you a container to store your urine sample in.

The test involves collecting all your pee over a 24-hour period in one container. You'll store the container in a fridge or cooler with ice in between collections. Then you'll take the container back to the lab.

Occasionally, your doctor may ask you to collect one sample of urine in the morning, as opposed to a 24-hour collection.

This test checks how well your adrenal glands respond to the adrenocorticotropic hormone (ACTH). This hormone is produced in the pituitary gland and stimulates the adrenal glands to release cortisol. The ACTH test is usually given along with the cortisol test when your doctor thinks you might have an adrenal gland problem due to low cortisol levels in your body.

Here's how the test works:

Your blood is drawn.

Then you get a shot of synthetic ACTH hormone.

After 30 or 60 minutes (depending on how much ACTH you get), your blood is drawn again.

The lab checks your cortisol level.

Dexamethasone suppression test

This might be considered the reverse of the ACTH test and is usually given along with the cortisol test to find out why you have high levels of cortisol in your body and whether they can be suppressed. There are two main ways of doing the test.

Low dose overnight: You take 1 milligram (mg) of the steroid dexamethasone at 11 p.m. Next morning at 8 a.m., a lab test draws your blood to measure your cortisol level.

High dose overnight: Your cortisol is measured on the morning of the test. At 11 p.m., you take 8 mg of dexamethasone. Next morning at 8 a.m., your blood is drawn to measure your cortisol level.

Dexamethasone reduces the release of ACTH in healthy people. So if you take the steroid, the ACTH level should reduce as well as your cortisol level. But if your pituitary gland produces too much ACTH, the levels might still be too high with the low-dose test. They should return to normal with the high-dose test.

The low-dose test helps determine whether your body is producing too much ACTH, while the high-dose test can help the doctor decide whether the problem is due to Cushing's disease (a tumor in the pituitary gland) or a tumor happening in a different body part.

When the cause of Cushing's syndrome is a tumor in your pituitary, the condition is called Cushing's disease to differentiate it from the condition being caused by a tumor in another body part. Most cases of Cushing's syndrome are Cushing's disease.

Abnormal cortisol levels could be due to a variety of things, some less serious than others. These include:

A very high level of cortisol is often a sign of Cushing's syndrome, while a very low level can be a sign of Addison's disease or another adrenal gland issue. Cushing's and Addison's are both rare diseases. 

A more common explanation for abnormal levels might be the use of steroids (for treating other illnesses or for bodybuilding), which can create high levels of cortisol. Also, stopping these drugs suddenly might cause low levels of cortisol.

Constant stress can also cause high levels of cortisol so taking stress-relief measures can bring the levels down.

In addition to the tests listed above, your doctor may order other blood tests to pinpoint the cause of your abnormal cortisol levels. Some things, such as abnormal growths or tumors, can affect them. If they suspect this may be the case, your doctor will order a CT scan or an MRI.

A cortisol test measures the level of cortisol in your blood, urine, or saliva. If it's too high or too low, it might mean you have a disease. But many things can change your cortisol level, including stress and steroid medication.

Cortisol Test FAQs

How do I get my cortisol levels down?

If you have Cushing's syndrome or Addison's disease, you're going to need medication. In the case of Cushing's syndrome, if it's caused by a tumor, you might need surgery to remove the tumor followed by radiation. If you don't have a disease but just higher than normal levels of cortisol, you may be able to bring them down by getting proper sleep, exercising regularly, and reducing your stress.

Do you need to fast for a cortisol blood test?

No, you don't need to fast.