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 metabolism, immune response, and stress reactions.
["Free cortisol helps your body manage stress and maintain balance in key bodily functions."]
Key facts at a glance
- LOINC
- 102028-8
- Short code
- Cortis 3h p Gc SerPl-mCnc
- Synonyms
- Cortis 3h p Gc 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
- 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 (too much cortisol) or adrenal insufficiency (too little cortisol). It can also help diagnose issues with the pituitary gland or adrenal glands that affect hormone production.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it involves a blood draw. Avoid caffeine or stress-inducing activities for a few hours before the test to get more accurate results.
How the Test Is Performed
A healthcare provider will draw blood from a vein in your arm. The sample is sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels.
What the Results Mean
Results are compared to standard reference ranges, but your doctor will interpret them in the context of your symptoms and medical history. Abnormally high or low levels may signal underlying health issues that need further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Cortisol plays a vital role in regulating metabolism, immune function, and stress responses. Abnormal levels can indicate conditions such as adrenal dysfunction, Cushing’s syndrome, or pituitary disorders. Your doctor will use these results alongside other tests and symptoms to guide diagnosis and treatment.
Short name
Free Cortisol
Frequently asked questions
What causes abnormal cortisol levels?
How is cortisol tested differently from total cortisol?
Can diet or medications 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