Cortisol, Free, 24-Hour Urine, with 2 mg Dexamethasone Suppression, Mass Concentration
This test measures the amount of free (unbound) cortisol excreted in urine collected over 24 hours after a 2 mg dexamethasone dose, often used to screen for cortisol excess.
["It helps evaluate whether the body is overproducing cortisol and whether normal suppression occurs after dexamethasone."]
Key facts at a glance
- LOINC
- 1392-0
- Short code
- Cortis F 48h p 2 mg Dex 24h Ur-mCnc
- Synonyms
- Cortis F 48h p 2 mg Dex 24h Ur-mCnc
- Category
- hormone
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
Cortisol is a hormone made by the adrenal glands that helps regulate metabolism, blood pressure, and the stress response. Most cortisol in blood is bound to proteins; the "free" fraction is the active portion that filters into urine. A 24-hour urine collection captures the total free cortisol excreted over a full day.
Why Dexamethasone Is Given
Dexamethasone is a synthetic steroid that normally signals the body to reduce cortisol production. In a suppression test, a 2 mg dose is given so that a normal response shows reduced cortisol output. If cortisol remains elevated, it can suggest the body is not suppressing as expected.
How the Urine Collection Works
You will typically collect all urine produced over a 24-hour period into a provided container, following your care team's specific start and stop instructions. The dexamethasone dose is taken as directed, often at a set time before or during collection. Timing is important, so follow instructions carefully and keep the container refrigerated if advised.
What Results Can Mean
Results are interpreted alongside your symptoms, medications, and other tests. A value that fails to suppress after dexamethasone may prompt further evaluation, while a normal suppression response is generally reassuring. No single result makes a diagnosis on its own.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is used to screen for conditions of cortisol excess, such as Cushing syndrome, and to assess whether the normal feedback that reduces cortisol after a steroid dose is working. It is interpreted in the context of the patient's clinical picture; conditions, medications, pregnancy, and collection errors can affect results, so abnormal findings usually require confirmation with additional testing.
Short name
24-hr Urine Free Cortisol (2 mg DST)
Frequently asked questions
Do I need to avoid any medications before this test?
What happens if I miss some urine during the 24-hour collection?
Is a single abnormal result a diagnosis?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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