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Serum/Plasma Free Cortisol Concentration (24-Hour Urinary Excretion)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of cortisol naturally produced by your body over a full day, collected in your urine. It helps assess whether your adrenal glands are functioning properly to regulate stress hormones.

Quick summary

["This test helps diagnose conditions like Cushing’s syndrome or adrenal insufficiency by checking cortisol levels over time."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
60659-0
Short code
GL'-SN/Face low Skull XR
Synonyms
GL'-SN/Face low Skull XR
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr-measured
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Matters for Your Health

Cortisol is a hormone that helps your body respond to stress and maintain balance. High levels over time can signal overproduction (e.g., from tumors or excess steroid use), while low levels may indicate problems with your adrenal glands. This test provides a full picture of cortisol activity, unlike a single blood draw.

How the Test Works

You’ll collect urine samples throughout the day in a special container. Each sample is sent to the lab, where cortisol is measured in your urine. The results are compared to typical patterns to identify any abnormalities.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications that could affect cortisol levels (like some steroids). Drink plenty of water to help your kidneys collect urine properly.

Common Conditions This Test Helps Diagnose

This test is often used to diagnose conditions like Cushing’s syndrome (too much cortisol), adrenal insufficiency (too little cortisol), or to monitor treatment for hormone-related disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

24-Hour Urinary Free Cortisol

Frequently asked questions

What does a high result mean?
A high result may suggest conditions like Cushing’s syndrome, where your body produces too much cortisol, or long-term use of certain medications. Your doctor will review your symptoms and other test results to determine the cause.
What does a low result mean?
A low result might indicate adrenal insufficiency, where your adrenal glands aren’t producing enough cortisol. This can happen after surgery, infection, or long-term steroid use. Your doctor will discuss further testing or treatment options with you.
How often will I need this test?
The frequency depends on your symptoms and medical needs. Your doctor may recommend this test periodically if you have a history of hormone-related conditions or are being treated for stress-related disorders.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy