What is this test?
This timed test measures cortisol reported from urine collected over a full day. Collecting every urine portion is essential because the laboratory calculates a daily total rather than interpreting one spot sample.
Why might it be ordered?
- To investigate suspected excess cortisol when this timed method is appropriate.
- To monitor a known condition when your clinician needs a full-day excretion measurement.
What sample is needed?
All urine passed during the laboratory-defined 24-hour period is required. Use only the container supplied or approved by the laboratory.
How should you prepare?
Follow the laboratory protocol exactly. Usually you discard the first morning urine and record that time, collect every portion through the day and night, then include the urine passed at the same time the next morning. Confirm container, preservative, storage and whether the test is urinary free cortisol. Do not change steroid medicines on your own.
How should you understand the result?
Stress, sleep, medicines and collection problems can affect the result. Confirm whether the laboratory reports urinary free cortisol and which method it uses.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.
- Laboratory Tests — MedlinePlus, U.S. National Library of Medicine
- How to Prepare for a Lab Test — MedlinePlus, U.S. National Library of Medicine
- How to Understand Your Lab Results — MedlinePlus, U.S. National Library of Medicine
- 24-hour urine collection — MedlinePlus, U.S. National Library of Medicine