Cortisol (Serum) – 24-Hour Urinary Free Cortisol

Why This Test Is Done

Your doctor may order a 24-hour urine cortisol test if they suspect conditions affecting your adrenal glands, such as Cushing’s syndrome (too much cortisol) or adrenal insufficiency (too little cortisol). It’s also used to monitor treatment responses for these conditions or to investigate unexplained weight changes, fatigue, or high blood pressure.

How the Test Works

You’ll collect all your urine for a full 24-hour period in a special container. The test measures cortisol levels in your urine, which reflects your body’s natural cortisol production over time. Unlike a single blood test, this method provides a more complete picture of daily cortisol levels.

Sample Collection

To prepare, empty your bladder before starting and discard the first urine sample. Collect every urine sample for the next 24 hours, including overnight. Store samples at room temperature and return them to your lab on the same day or refrigerate until pickup. Follow your lab’s specific instructions carefully to ensure accuracy.

What to Expect After the Test

After collection, your urine will be sent to a lab for analysis. Results take time to process, often 1–2 weeks. Your doctor will review the results with you, discussing any findings and next steps, such as further testing or treatment adjustments.