Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of the hormone cortisol found naturally in your blood. Free cortisol is the active form that helps regulate metabolism, immune response, and stress reactions.
["Free cortisol levels help assess your body’s stress response and hormone balance."]
Key facts at a glance
- LOINC
- 25619-8
- Short code
- Cortis sp2 p chal SerPl-sCnc
- Synonyms
- Cortis sp2 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 Is This Test Done?
Your doctor may order a free cortisol test to check for conditions like Cushing’s syndrome (overactive cortisol production) or adrenal insufficiency (underactive cortisol production). It can also help diagnose issues related to stress, pituitary gland problems, or hormone imbalances.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw. If you’re taking medications that affect cortisol levels, your doctor will let you know if you should stop them temporarily.
What Happens During the Test?
A healthcare provider will draw blood from a vein in your arm. The blood sample will be sent to a lab for analysis. Free cortisol is measured using a sensitive immunoassay method to detect its presence in your serum.
What Do Results Mean?
Results are compared to reference ranges for healthy individuals, but exact values can vary by lab. High or low levels may signal underlying health concerns that need further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Free cortisol is a key hormone in the body’s stress response system. Elevated levels may indicate conditions like Cushing’s syndrome, while low levels can signal adrenal insufficiency or problems with the pituitary gland. This test helps doctors diagnose and monitor these conditions by providing precise measurements of your body’s natural cortisol production.
Short name
Free Cortisol
Frequently asked questions
What does a free cortisol test measure?
How is the test different from a total cortisol test?
Can I eat or drink before 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