Cortisol, Free (Serum)
This test measures the amount of free cortisol, a hormone produced by your adrenal glands, in your blood. Free cortisol is the active form of the hormone that travels freely in your bloodstream and isn’t bound to proteins.
["Understanding your free cortisol levels helps assess adrenal function and potential hormone-related conditions."]
Key facts at a glance
- LOINC
- 47605-1
- Short code
- Cortis 15M p 1 ug/kg CRH IV SerPl-sCnc
- Synonyms
- Cortis 15M p 1 ug/kg CRH IV 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
- CPT
- 86701
- 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 Is Done
Your healthcare provider may order this test to diagnose or monitor conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or other hormonal imbalances. It can also help evaluate symptoms such as unusual weight changes, fatigue, or mood swings that might be linked to cortisol levels.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if cortisol levels are measured at specific times of day. If your test is part of a 24-hour urine collection, follow your provider’s instructions carefully to ensure accurate results.
How the Test Is Performed
A blood sample is drawn from a vein in your arm by a healthcare professional. The sample is sent to a lab for analysis using an immunoassay method to detect free cortisol levels.
What the Results Mean
Results are typically reported as a concentration value (e.g., micrograms per deciliter). While reference ranges vary by lab, higher or lower-than-expected levels may signal underlying health concerns that need further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels help diagnose conditions like Cushing’s syndrome (elevated cortisol) or Addison’s disease (low cortisol). Abnormal results may prompt additional testing, such as a saliva cortisol test or 24-hour urine cortisol collection, to confirm a diagnosis or guide treatment decisions.
Short name
Free Cortisol
Frequently asked questions
How often should I get this test?
What are typical symptoms that might lead to this test?
Can lifestyle changes affect cortisol test results?
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