What is a Cortisol Test?
A cortisol test measures the level of cortisol in your blood, urine, or saliva to see if your levels are normal. Cortisol is a hormone that affects almost every organ and tissue in your body. It helps your body:
- Respond to stress (cortisol is sometimes called the "stress hormone")
- Reduce inflammation
- Regulate blood sugar and metabolism (how your body uses food for energy)
- Control blood pressure
Cortisol is made by your adrenal glands, two small glands that sit above the kidneys. A gland in your brain, called the pituitary gland, makes a hormone that tells your adrenal glands how much cortisol to make. If your cortisol levels are too high or too low, it may mean you have a disorder of your adrenal glands, a problem with your pituitary gland, or a tumor that makes cortisol.
High levels of cortisol may also happen if you take large doses of certain steroid medicines, such as prednisone, for a long time. And low levels may happen if you stop the medicine suddenly.
Without treatment, cortisol levels that are too high or too low can be very serious.
Other names: urinary cortisol, salivary cortisol, free cortisol, blood cortisol, plasma cortisol
What is it used for?
A cortisol test is used to help diagnose medical conditions that cause too much or too little cortisol. These conditions include disorders that affect the adrenal glands:
- Cushing's syndrome is a disorder that happens when your body has too much cortisol over a long period of time.
- Addison disease is a condition in which your adrenal glands are damaged and can't make enough cortisol.
- Secondary adrenal insufficiency is a condition in which your adrenal glands don't make enough cortisol because your pituitary gland isn't working properly.
Cortisol testing is also used to monitor treatment for these conditions.
Why do I need a cortisol test?
You may need a cortisol test if you have symptoms of a condition that affects cortisol levels.
- Symptoms of Cushing's syndrome (too much cortisol) may include:
- Weight gain
- Thin arms and legs
- Round face
- Increased fat around the base of the neck or between the shoulder blades
- Easy bruising
- Wide purple streaks on the stomach, breasts, hips, and under the arms
- Muscle weakness
- Common symptoms of Addison disease and adrenal insufficiency (not enough cortisol) may include:
What happens during a cortisol test?
A cortisol test often uses a sample of blood drawn at a lab. But the test may also be done on urine or saliva collected at home. Normally, cortisol levels vary during the day, so your provider may order more than one type of test to get more information about your cortisol levels.
For a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Blood samples are usually taken twice during the day--once in the morning when cortisol levels are at their highest, and again around 4 p.m., when levels are much lower.
For a cortisol urine test, your provider may ask you to collect all your urine during a 24-hour period. This is called a "24-hour urine sample test." For this test, you'll be given a special container and instructions for how to collect and store your urine sample. Your provider will tell you what time to start. The test usually includes the following steps:
- To begin, urinate in the toilet as usual. Do not collect this urine. Write down the time you urinated.
- For the next 24 hours, collect all your urine in the container.
- Store the urine container in a refrigerator or in a cooler with ice during the collection period.
- 24 hours after starting the test, try to urinate if you can. This is the last urine collection for the test.
- Return the container with your urine to your provider's office or the laboratory as instructed.
In certain cases, a urine test for cortisol may be done on one sample of urine collected in the morning.
A cortisol saliva test is usually done at home with a kit to collect a saliva sample. Your provider will tell you what time to collect your sample. It's often done at night before you go to bed when cortisol levels are normally lower.
Most kits include a swab and a container to store it. Be careful to follow the instructions that come with your kit. They usually include these general steps:
- Do not eat, drink, brush, or floss your teeth for 30 minutes before the test.
- Wash and dry your hands.
- Open the tube that holds the swab and let the swab fall into your mouth without touching it with your hands.
- Roll the swab in your mouth or hold it under your tongue for about 2 minutes until it is soaked with saliva.
- Spit the swab back into the tube without touching it and close the tube.
- Label the tube with the time you collected the sample.
- Take your saliva sample to your doctor's office or the lab the next day as instructed.
Will I need to do anything to prepare for the test?
The preparations will depend on the type of test you are having. Be sure to follow all the instructions that your provider gives you.
Stress can raise your cortisol levels, so you may need to rest before your test. A blood test will require you to schedule two appointments at different times of the day. Before a saliva test, you may need to stop using certain medicines. Let your provider know about all medicines you use, including skin creams. But don't stop using any medicines without talking with your provider first.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
There are no known risks to a urine or saliva test.
What do the results mean?
A cortisol test alone can't diagnose the cause of abnormal cortisol levels. If your cortisol level isn't normal, you will usually have more tests to find out what is causing the problem.
High levels of cortisol may be a sign that you have Cushing's syndrome. It may be caused by:
- Taking high doses of certain steroid medicines for a long time to treat conditions, such as asthma, rheumatoid arthritis, and lupus
- Tumors in your pituitary gland or other parts of your body that make too much of the hormone that tells your adrenal glands to make cortisol
- Tumors in your adrenal glands that make extra cortisol
Low levels of cortisol may mean you have Addison disease or secondary adrenal insufficiency:
- Common causes of Addison's disease include damage to the adrenal glands from conditions, such as:
- Common causes of secondary adrenal insufficiency include:
- Autoimmune diseases
- Problems with the pituitary gland
- Traumatic brain injury
The most common cause of low cortisol levels is suddenly stopping steroid medicines after using them for a long time.
If your cortisol results aren't normal, it doesn't always mean you have a medical condition that needs treatment. Cortisol levels can be affected by:
- Serious illness
- Hot and cold temperatures
- Certain thyroid diseases
- Certain medicines, such as birth control pills
To learn what your test results mean, talk with your health care provider.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a cortisol test?
A cortisol test is one of the tests that may be used to help diagnose congenital adrenal hyperplasia (CAH). CAH is a group of inherited disorders in which the adrenal glands don't make enough cortisol.
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