Cortisol, Free (Serum/Plasma)
This test measures the amount of free cortisol, a hormone produced by your adrenal glands that helps regulate metabolism, immune response, and stress reactions.
Free cortisol helps assess adrenal function and potential hormone imbalances.
Key facts at a glance
- LOINC
- 58653-7
- Short code
- Cortis 1h p 1 ug/kg CRH IV Sal-sCnc
- Synonyms
- Cortis 1h p 1 ug/kg CRH IV Sal-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 Is This Test Done?
Your doctor may order a free cortisol test to evaluate conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to monitor treatment for hormone-related disorders. It can also help diagnose issues with cortisol metabolism or stress responses.
What Does the Result Mean?
Results are interpreted based on your symptoms, medical history, and other test results. Elevated levels may suggest Cushing’s syndrome or other causes of high cortisol, while low levels could indicate adrenal insufficiency or problems with cortisol production.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The sample is collected in a special tube to separate serum or plasma, which is then sent to a lab for analysis using a sensitive immunoassay method to detect cortisol levels.
What Are Common Causes of Abnormal Results?
High cortisol levels may be linked to prolonged stress, certain medications (like steroids), tumors affecting the adrenal glands or pituitary, or conditions like hyperthyroidism. Low cortisol levels may result from adrenal gland damage, autoimmune disorders, or severe stress.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Free cortisol testing is critical for diagnosing and managing hormonal imbalances that affect daily functions, stress tolerance, and overall health. It helps differentiate between conditions like Cushing’s syndrome, Addison’s disease, or pseudohypercortisolism, guiding appropriate treatment plans.
Short name
Free Cortisol
Frequently asked questions
Why might my doctor recommend this test if I have symptoms like weight gain, fatigue, or high blood pressure?
What should I do if my cortisol test results are abnormal?
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