Cortisol, Serum, Free (24-hour Urine Collection)

Why This Test Is Done

Your doctor may order a 24-hour urine cortisol test if they suspect conditions like Cushing’s syndrome (too much cortisol) or adrenal gland problems (like Addison’s disease). It’s also used to monitor treatment responses for these conditions. Unlike blood tests, this method captures cortisol levels throughout the day without interference from other substances in your blood.

What to Expect Before the Test

You’ll need to collect all urine for a full 24-hour period, starting right after you wake up and ending just before you wake up the next morning. Keep the urine in a refrigerator or cool container, and bring all samples to your lab on the following day. Follow your doctor’s instructions carefully to ensure accurate results.

How the Test Works

The test measures free cortisol, which is the active form of the hormone. Unlike blood cortisol, urine cortisol reflects daily hormone production without being influenced by stress-related spikes in your bloodstream. The lab analyzes the collected urine sample to determine the total cortisol excreted over 24 hours.

What the Results Mean

Results are compared to standard ranges for healthy adults, but exact values can vary by lab. High levels may indicate Cushing’s syndrome or other causes of excess cortisol, while low levels could signal adrenal insufficiency or other hormonal imbalances. Your doctor will interpret the results in the context of your symptoms and medical history.