What Is a Cortisol Test?

Cortisol is a hormone that is important throughout the body to maintain blood pressure, blood sugar, metabolism, and respond to infections and stress.. Your doctor may want you to be tested to see if you have the right level of cortisol in your blood.

Cortisol is made by your adrenal glands -- two small glands that sit on top of your kidneys. Along with helping you respond to stress, it also plays a key role in other functions, including how your body breaks down carbohydrates, lipids, and proteins.

Tests can detect whether you have a condition called Cushing syndrome, which involves having too much of the hormone. It can also check for Addison's disease, which is caused by having too little. The tests also help screen for other diseases that affect your pituitary and adrenal glands.

Your doctor might order a cortisol test if he sees symptoms that suggest your levels are either too high or too low.

Your cortisol blood level can be measured in three ways -- through your blood, saliva, or urine.

Blood Test

Often, this test is done twice in 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 in the course of a 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.

Saliva Test

Studies show this the saliva test is about 90% accurate in diagnosing Cushing syndrome.

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.

You can purchase salivary cortisol tests at drugstores. But for the most accurate results, see your doctor to have it done. He might want to compare the result against other tests.

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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 you doctor prescribes a urine test, you’ll need to provide a 24-hour sample. This means you’ll pee into a special container or bag every time you need to use the bathroom over the course of a full day.

Further Testing

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, like abnormal growths or tumors, can affect them. If he suspects this may be the case, your doctor will order a CT scan or an MRI.

WebMD Medical Reference Reviewed by Louise Chang, MD on December 22, 2018

Sources

SOURCES:

American Association for Clinical Chemistry: “Cortisol Test.”

National Institutes of Health: “Adrenal Gland Disorders: Condition Information.”

University of Rochester Medical Center: “Cortisol (Blood),” “Cortisol (Urine).”

Cushing’s Support and Research Foundation: “Diagnostic Testing for Cushing’s Syndrome.”

PubMed: “Measurement of Salivary Cortisol in 2012 – Laboratory Techniques and Clinic Indications.”

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