Cortisol, Serum (Free)
This test measures the amount of free (unbound) cortisol in your blood, a hormone produced by your adrenal glands that helps regulate stress responses, metabolism, and other bodily functions.
["Free cortisol helps assess adrenal gland function and potential stress-related hormone imbalances."]
Key facts at a glance
- LOINC
- 25622-2
- Short code
- Cortis sp4 p chal SerPl-sCnc
- Synonyms
- Cortis sp4 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 Is Done
Your healthcare provider may order a free cortisol test to diagnose conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to evaluate chronic stress responses. It can also help monitor treatment effectiveness for hormone-related disorders.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if timing is critical for accurate results. Avoid caffeine or alcohol for 24 hours beforehand, as they can affect cortisol levels.
How the Test Is Performed
A blood sample is taken from a vein in your arm by a healthcare professional. You may feel a brief pinch, but the process is quick and usually painless. The sample is sent to a lab for analysis using a sensitive immunoassay method to detect free cortisol levels.
What the Results Mean
Results are interpreted based on your clinical symptoms and other lab values. Elevated free cortisol may indicate conditions like Cushing’s syndrome, while low levels could signal adrenal insufficiency or other stress-related disorders. Your provider will discuss findings with you.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol testing is critical for diagnosing and managing hormonal imbalances tied to stress, metabolism, and adrenal gland function. It helps differentiate between conditions like primary adrenal insufficiency (Addison’s disease), secondary adrenal insufficiency, or ectopic ACTH syndrome (hormone-producing tumors). Elevated cortisol may also signal chronic stress or iatrogenic causes (e.g., steroid medications).
Short name
Free Cortisol
Frequently asked questions
What causes abnormal cortisol levels?
How often should I get 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