A cortisol test is usually in the form of a blood test. During 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.
Because cortisol levels change throughout the day, the timing of a cortisol test is important. A cortisol blood test is usually done twice a day–once in the morning when cortisol levels are at their highest, and again around 4 p.m., when levels are much lower.
Cortisol may also be measured in a urine or saliva test. For a cortisol urine test, your health care provider may ask you to collect all urine during a 24-hour period. This is called a "24-hour urine sample test." It is used because cortisol levels vary throughout the day. For this test, your health care provider or a laboratory professional will give you a container to collect your urine and instructions on how to collect and store your samples. A 24-hour urine sample test usually includes the following steps:
- Empty your bladder in the morning and flush that urine away. Record the time.
- For the next 24 hours, save all your urine passed in the container provided.
- Store your urine container in the refrigerator or a cooler with ice.
- Return the sample container to your health provider's office or the laboratory as instructed.
A cortisol saliva test is usually done at home, late at night, when cortisol levels are lower. Your health care provider will recommend or provide you with a kit for this test. The kit will likely include a swab to collect your sample and a container to store it. Steps usually include the following:
- Do not eat, drink, or brush your teeth for 15-30 minutes before the test.
- Collect the sample between 11 p.m. and midnight, or as instructed by your provider.
- Put the swab into your mouth.
- Roll the swab in your mouth for about 2 minutes so it can get covered in saliva.
- Don't touch the tip of the swab with your fingers.
- Put the swab into the container within the kit and return it to your provider as instructed.