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Patient Guide: 24-Hour Urine Cortisol Collection for Cushing’s Syndrome Diagnosis

Patient Guide: 24-Hour Urine Cortisol Collection for Cushing’s Syndrome Diagnosis
March 19, 2025

A 24-hour urine collection (also known as a urinary free cortisol test or UFC) is an essential diagnostic tool used to measure cortisol levels—especially when evaluating for Cushing’s syndrome or episodic Cushing’s disease. This guide will walk you through why this test matters, how to complete it correctly, and how to understand your results.

What Is Cortisol and Why Test It?

Cortisol is a hormone produced by your adrenal glands, often released in response to stress (also known as the “fight or flight” hormone). In patients with Cushing’s syndrome, the body produces too much cortisol, which can lead to a wide variety of symptoms—from weight gain and insomnia to fatigue and high blood pressure.

Episodic Cushing’s Disease: Why Multiple Tests Matter

Unlike classic cases where cortisol is consistently elevated, episodic (or periodic) Cushing’s disease means cortisol levels spike on some days and appear normal on others. Dr. Theodore Friedman, a leading Cushing’s specialist, emphasizes the importance of multiple UFC tests and salivary cortisol tests to catch these intermittent spikes.

In a 2010 study published in Hormone and Metabolic Research, Dr. Friedman found that 65 out of 66 patients with Cushing’s had at least one normal cortisol test result. This is why multiple collections are often needed, especially during suspected “high cortisol” periods.

How to Collect a 24-Hour Urine Sample (Quest & LabCorp)

Follow these steps carefully to ensure accurate results:

  1. Start at 8:00 AM (or consistent morning time):
    • On Day 1, void your bladder and discard this urine. Do not collect this sample.
  2. Begin collection:
    • Use a lab-provided jug marked for 24-hour urine volume (often containing a preservative like boric acid).
  3. Collect all urine for the next 24 hours:
    • Keep the jug refrigerated between voids.
  4. Final sample:
    • On Day 2 at 8:00 AM, collect your first morning urine and add it to the jug.
  5. Label the jug:
    • Include your full name, date of birth, and start/end times.
  6. Document total urine volume:
    • Write it on the lab requisition and ensure the lab records it too.
  7. Freeze if needed:
    • If unable to drop off the sample within 48 hours, freeze it to preserve cortisol stability.
  8. Drop off at a certified LabCorp or Quest location:
    • Use their websites or call ahead to confirm hours and specimen drop-off policies.

Lab Contact Info:

What About 17-Hydroxysteroids (17-OHS)?

In addition to UFC, Dr. Friedman often orders 24-hour urine 17-hydroxysteroids (17-OHS) to detect cortisol metabolites, which can be elevated in mild or episodic Cushing’s even when UFC levels are normal.

  • Test Code for 17-OHS:
    • Quest: 0070490
    • LabCorp: 806730
  • Normal Range: 4–14 mg/day
  • Dr. Friedman uses the 17-OHS/day result, not the creatinine-adjusted value (17-OHS/Cr).

If the lab tells you this test is unavailable, request that the staff contact their supervisor or customer service—it is still performed and sent to ARUP labs.

How Long for Results?

Results typically take 2 weeks. You can access them through the Quest or LabCorp patient portals. Dr. Friedman recommends collecting all required 24-hour urine and salivary cortisol samples before scheduling your follow-up to ensure a comprehensive review.

Recognizing High vs. Low Cortisol Days

For accurate diagnosis, it’s important to test on both “high” and “low” cortisol days. Here’s how to tell the difference:

Signs of a High Cortisol Phase:

  • Wired at night or trouble sleeping
  • Unexplained weight gain
  • Acne or oily skin
  • Anxiety or irritability
  • Euphoria or bursts of energy
  • Feeling physically better than usual
  • High blood pressure or blood sugar
  • Swelling or water retention (edema)
  • Energy peaks after sunset
  • Rapid speech or racing thoughts

Helpful Tip: If you have diabetes, use a continuous glucose monitor (CGM). If not, consider over-the-counter options like Stelo or Lingo to detect nighttime glucose spikes, which may indicate a cortisol “high.”

Signs of a Low Cortisol Phase:

  • Fatigue or exhaustion
  • Nausea or loss of appetite
  • Depression or mood lows
  • Muscle or joint pain
  • Weight loss

Track how you feel each day you test. Noting symptoms can help identify cortisol patterns and guide future test timing.

Final Thoughts

Diagnosing episodic or mild Cushing’s syndrome can be a long and sometimes frustrating journey, but accurate and consistent urine cortisol testing is critical. Be patient, keep detailed notes, and work closely with your endocrinologist to uncover patterns that lead to a diagnosis.

Need Help?

  • Contact LabCorp or Quest for questions about specimen pickup or test processing.
  • Dr. Friedman’s office is also available to guide you through this process during your evaluation.
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