Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Cortisol helps regulate metabolism, immune response, and stress reactions.
["Free cortisol levels help assess adrenal function and potential stress-related hormone imbalances."]
Key facts at a glance
- LOINC
- 58672-7
- Short code
- Cortis 45M p 1 ug/kg CRH IV SerPl-sCnc
- Synonyms
- Cortis 45M 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 Might Be Ordered
Your doctor may recommend this test if you have symptoms like unexplained weight changes, fatigue, mood swings, or signs of adrenal insufficiency or hyperactivity. It could also be used to evaluate conditions like Cushing’s syndrome, adrenal tumors, or to monitor treatment for hormone-related disorders.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8 hours before the test if cortisol is measured at specific times (e.g., morning or evening). Bring any medications you’re currently taking to your appointment.
How the Test Works
A blood sample is drawn from a vein in your arm. The sample is processed to measure free cortisol levels using a sensitive immunoassay method, which detects the hormone without interference from other substances in the blood.
What the Results Mean
Results are compared to reference ranges for free cortisol, which can vary slightly by lab. High levels may indicate conditions like Cushing’s syndrome, while low levels could signal adrenal insufficiency or other stress-related disorders. Your doctor 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 testing is critical for diagnosing and managing conditions tied to adrenal hormone imbalances. Elevated cortisol may point to overproduction by the adrenal glands or prolonged stress, while low levels can signal adrenal gland dysfunction or other endocrine disorders. Early detection helps guide treatment, such as medication adjustments or lifestyle changes.
Short name
Free Cortisol
Frequently asked questions
What causes cortisol levels to be tested?
How often should I get this test?
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