Cortisol Test: Purpose, Preparation, Procedure, Results and Outlook

Updated: September 25, 2021

Cortisol is a steroid hormone produced by the adrenal glands when you are under stress. Adrenal glands are two small glands that sit on top of your kidneys. Cortisol is the main hormone involved in stress and fight-or-flight response. This is a natural and protective response to a perceived threat or danger. 

Whenever you experience something your body perceives as a threat, a chemical known as adrenocorticotropic hormone (ACTH) is released in your brain. This triggers your adrenal glands to release cortisol and adrenaline. Increased levels of cortisol result in a burst of new energy and strength. It also plays a key role in other functions, including how your body breaks down carbohydrates, lipids, and proteins.  In the fight-or-flight response, cortisol suppresses any functions that are unnecessary that response which may include a rapid heart rate, dry mouth, stomach upset, diarrhea or getting panic. Cortisol release also suppresses your growth processes, digestive system and reproductive system. It can also changes how your immune system responds. Your cortisol blood level can be measured in three ways which could be through your blood, saliva, or urine.

Purpose of Cortisol Level Test:

The cortisol level test is done to check if your cortisol production levels are either too high or too low. There are certain diseases, such as Addison's disease and Cushing's disease, which affect the amount of cortisol your adrenal glands produce.
Cushing's syndrome, involves having too much of the hormone, where as for Addison's disease, is caused by having too little of cortisol. The test is used in the diagnosis of these diseases. The tests also help screen for other diseases that affect your pituitary and adrenal glands by assessing the functioning of these glands. Cortisol plays an important role in several systems in the body. These systems include:

• stress responses
• immune system
• nervous system
• circulatory system
• skeletal system
• the breakdown of proteins, fats, and carbohydrates

Preparation for the Cortisol Level Test:

Cortisol levels vary throughout the day, but they are usually highest in the morning. This is the reason to perform this test in the morning. You don't need to fast for a cortisol test. There are certain drugs that affect cortisol levels. Therefore it is recommended not to take these drugs before the test is done. Cortisol levels are sometimes increased by:

• drugs containing estrogen
• synthetic glucocorticoids, such as prednisone
• pregnancy
• Cortisol levels are sometimes decreased by:
• drugs containing androgens
• phenytoin

Cortisol levels can also be affected by physical stress, emotional stress, and illness which is due to the increased release of ACTH by the pituitary gland during the normal stress response.

Procedure for the Cortisol Level Test:

By doing this the flow of blood in the arm is stopped and the veins in your arm become more visible, which makes it easier to insert the needle. Alcohol is used to clean the site on your skin where the needle will be inserted and then the needle is inserted into the vein. This may cause a brief pinching or stinging sensation.
Your blood is collected in a tube that is attached to the needle. Sometimes more than one tube may be needed. The elastic band is removed after enough blood has been collected. Cotton or gauze is placed on the site of the needle insertion after the needle is removed from your skin. You will be asked to apply pressure to the area using cotton or gauze to stop bleeding. A bandage is used to secure the cotton or gauze after sometime in that place.
Often this test is done twice in the same day. Once in the morning, and again later in the afternoon, around 4 p.m. Because cortisol levels change a lot in the course of a day, this will give a clear idea.
Your results will show the level of cortisol in your blood at the time of the test. If your level is too high, other tests (urine or saliva) can be done to make sure the results aren't due to stress or a medication that acts like cortisol in your body.

Saliva Test:

the saliva test is about 90% accurate in diagnosing Cushing's syndrome. Because cortisol levels tend to be lowest between 11 p.m. and midnight, this test is done at night, before you go to bed. A high cortisol level near midnight can signal a disorder. Just spit into a small test tube provided by your doctor during the test to get a sample and the tubes will be send to the lab for analysis. Your results should be ready in a couple of weeks.

Urine Test:

This test is also called as free cortisol. This means the cortisol isn't bound to a protein as in blood tests measure. If you doctor prescribes a urine test, you will need to provide a 24-hour sample of urine. This means you will need to collect your urine in a special container or bag every time you need to use the bathroom over the course of a full day. This sample will then be tested the next day to see the results.

Results of the cortisol level test:

Normal results for a blood sample taken at 8 a.m. range between 6 and 23 micrograms per deciliter (mcg/dL). However, as many laboratories have different measuring techniques, the range may vary.
Higher than normal cortisol levels may indicate that:

• your pituitary gland is releasing too much ACTH due to a tumor or excess growth of the pituitary gland
• you have a tumor in your adrenal gland, resulting in excess cortisol production
• you have tumor elsewhere in your body that is involved in cortisol production

Lower than normal cortisol levels may indicate that:

• you have Addison's disease, which occurs when production of cortisol by your adrenal glands is too low
• you have hypopituitarism. Because the pituitary gland is not sending proper signals, production of cortisol by your adrenal glands is too low in this condition.

Outlook of the cortisol level test:

Some more tests should be done if the levels of cortisol in your blood are too high or too low. These may include a CT scan or an MRI which will help identifying abnormal growths or tumors.