Cortisol, Free, 24-Hour Urinary

Why This Test Matters

Cortisol is a hormone produced by your adrenal glands, which sit on top of your kidneys. It helps your body respond to stress, supports metabolism, and regulates blood pressure and immune function. Free cortisol is the active form that circulates in your blood and is excreted in urine. Measuring it over 24 hours gives a more accurate picture of your cortisol production than a single blood test.

What to Expect Before the Test

No special preparation is needed for this test. You’ll collect your urine for 24 hours, starting and ending with your first morning urine. Store the urine in a refrigerator or freezer until you return it to the lab. Follow your healthcare provider’s instructions carefully to ensure accurate results.

How the Test Works

Your urine sample is analyzed to measure the total amount of free cortisol excreted. The test uses a sensitive method to detect cortisol, which may include immunoassay or chromatography techniques. This helps determine if your cortisol levels are consistently high or low over time.

Possible Conditions or Concerns

Elevated cortisol levels may suggest conditions like Cushing’s syndrome (overproduction of cortisol) or certain tumors. Low cortisol levels could indicate adrenal insufficiency or other hormonal imbalances. This test helps differentiate between these possibilities and guides treatment decisions.