Cortisol, Serum (Free)
This test measures the amount of free (unbound) cortisol, a hormone produced by your adrenal glands that helps regulate stress responses, metabolism, and other bodily functions.
["Free cortisol helps assess adrenal function and potential hormone imbalances."]
Key facts at a glance
- LOINC
- 25628-9
- Short code
- Cortis sp9 p chal SerPl-sCnc
- Synonyms
- Cortis sp9 p chal SerPl-sCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like unexplained weight changes, fatigue, mood swings, or signs of high or low cortisol levels. It could also be used to diagnose conditions such as Cushing’s syndrome or adrenal insufficiency.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if cortisol levels are being measured at specific times (e.g., morning or evening). Bring any medications you’re taking to discuss with your provider.
How the Test Is Performed
A blood sample is taken from a vein in your arm by a healthcare professional. The blood is sent to a lab for analysis using a sensitive immunoassay method to detect cortisol levels.
What the Results Mean
Results are compared to reference ranges for free cortisol in serum, but exact values can vary by lab. Elevated levels may suggest conditions like Cushing’s syndrome, while low levels could indicate adrenal gland issues or other hormonal disorders.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol testing is critical for diagnosing and managing conditions tied to adrenal hormone dysfunction. Abnormal results may prompt further evaluation, such as additional cortisol tests (e.g., 24-hour urine cortisol or dexamethasone suppression tests) or imaging studies to identify underlying causes.
Short name
Free Cortisol
Frequently asked questions
What causes false high or low cortisol results?
How long does it take to get results?
Can I take medications before the test?
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