24-Hour Urine Free Cortisol Test

A cortisol urine test measures the total amount of cortisol, a key stress hormone, that your body removes through urine over a full 24 hours. Your doctor may order this test to help diagnose Cushing syndrome, a condition in which the body produces too much cortisol, or to check for adrenal insufficiency, where too little is made. Because cortisol levels rise and fall during the day, a 24-hour collection gives a more complete picture than a single blood sample.

Your doctor may recommend this test if they suspect conditions affecting your adrenal glands, such as overproduction of cortisol (e.g., Cushing’s syndrome) or underproduction (e.g., Addison’s disease). It’s also used to evaluate chronic stress responses or rule out certain pituitary disorders.

Cortisol is produced by your adrenal glands, two small glands located on top of your kidneys. It helps control metabolism, blood pressure, immune response, and how your body responds to stress. Throughout the day, your kidneys filter cortisol from your blood into your urine. By collecting all of your urine for 24 hours, the laboratory can measure the total amount of cortisol your body produced and excreted during that entire period.

You’ll collect all urine for a full 24-hour period in a special container. The cortisol in your urine is measured to determine how much is excreted daily, reflecting your body’s natural cortisol levels over time.

For this test, you will collect every drop of urine you pass during a 24-hour period. You will usually begin in the morning by emptying your bladder into the toilet and writing down the exact time. After that, collect each urine sample in the special container your lab provides and keep it in a cool place, such as a refrigerator. Exactly 24 hours later, empty your bladder one last time into the container, then return the sample to the lab as directed.

You’ll start by emptying your bladder into the container at the beginning of the 24-hour period (e.g., midnight). After that, collect all urine—including midstream samples—until you return the container the next day. Do not miss any urine, even if you feel like you’re not producing much.

Before the test, your healthcare provider will give you detailed instructions, and it is important to follow them closely. You may be asked to avoid strenuous exercise and stressful situations the day before and during the collection period. Some medicines, including corticosteroids, birth control pills, and certain diuretics, can affect your results, so do not stop taking any medication unless your doctor tells you to. Drink fluids normally and tell your provider if you are pregnant or feeling unwell.

No special preparation is needed, but avoid taking any medications that could affect cortisol levels (e.g., some steroids or blood pressure drugs) unless your doctor approves. Drink plenty of water to help flush cortisol into your urine.