Cortisol, Free Serum
This test measures the amount of free cortisol, a hormone produced by your adrenal glands, in your blood. Free cortisol is the active form that circulates freely in your bloodstream.
["Free cortisol helps regulate stress responses and metabolism; abnormal levels may signal adrenal gland issues or other health concerns."]
Key facts at a glance
- LOINC
- 1442-3
- Short code
- Cortis 9h p 8 mg Dex SerPl-mCnc
- Synonyms
- Cortis 9h p 8 mg Dex 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 diagnose conditions like Cushing’s syndrome (overactive adrenal glands causing high cortisol) or adrenal insufficiency (underactive adrenal glands causing low cortisol). It can also help evaluate stress responses, hormone imbalances, or evaluate treatment effectiveness for conditions affecting cortisol levels.
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 timing your cortisol levels around a specific time of day is important. Bring any medications you’re currently taking to your appointment.
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 using an immunoassay method to measure free cortisol levels.
What Are Possible Results?
Results are compared to reference ranges that may vary slightly by lab. High cortisol levels may indicate conditions like Cushing’s syndrome, while low levels may suggest adrenal insufficiency or other hormonal 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 levels are critical for diagnosing conditions affecting the adrenal glands, such as Cushing’s syndrome (excess cortisol) or Addison’s disease (deficient cortisol). Elevated or low cortisol can also signal other health issues, including stress-related disorders, pituitary gland problems, or certain medications affecting hormone balance. Regular monitoring may be needed for chronic conditions or ongoing treatment adjustments.
Short name
Free Cortisol
Frequently asked questions
What does a free cortisol test measure?
How is cortisol different from other cortisol tests?
Can lifestyle changes affect cortisol levels?
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