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.