Cortisol, Free (Serum)
This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Free cortisol is important for regulating stress responses, metabolism, and other bodily functions.
["Free cortisol helps your body manage stress and maintain balance in your hormones."]
Key facts at a glance
- LOINC
- 46399-2
- Short code
- Cortis 2h p 1 ug/kg CRH IV SerPl-mCnc
- Synonyms
- Cortis 2h p 1 ug/kg CRH IV SerPl-mCnc
- 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 Might Be Ordered
Your healthcare provider may order a free cortisol test if you have symptoms of hormone imbalances, such as excessive stress, fatigue, weight changes, or unusual mood swings. It could also be used to diagnose conditions like Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol).
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to avoid certain medications or supplements that could affect results. If you’re taking corticosteroids (like prednisone), your provider may instruct you to stop temporarily or adjust timing. Drink plenty of water the day of the test to help your blood flow smoothly.
How the Test Is Performed
A blood sample is drawn from a vein in your arm by a healthcare professional. The sample is then sent to a lab for analysis using an immunoassay method to measure free cortisol levels.
What the Results Mean
Results are compared to standard reference ranges, but these can vary by lab. High cortisol levels may indicate conditions like Cushing’s syndrome, while low levels could suggest Addison’s disease or other hormonal issues. Your provider will interpret results in the context of your symptoms and medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol is a key hormone involved in stress response, immune function, and metabolism. Abnormal levels can signal underlying health conditions, such as hormonal imbalances, adrenal disorders, or even certain cancers. Regular monitoring may be needed if you have a history of these conditions or take medications that affect cortisol.
Short name
Free Cortisol
Frequently asked questions
What causes free cortisol levels to be high?
What causes free cortisol levels to be low?
How often should I get this 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