Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of the hormone cortisol, in your blood. Free cortisol is the active, unbound portion that circulates freely in your serum.
Free cortisol helps regulate stress responses and metabolism; abnormal levels may signal adrenal dysfunction or other health concerns.
Key facts at a glance
- LOINC
- 47604-4
- Short code
- Cortis 1.5h p 1 ug/kg CRH IV SerPl-sCnc
- Synonyms
- Cortis 1.5h 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 healthcare provider may recommend this test if you have symptoms like unexplained fatigue, weight changes, or mood swings that could relate to hormonal imbalances. It’s also used to diagnose conditions such as Cushing’s syndrome or Addison’s disease, or to monitor treatment for these conditions.
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 cortisol levels are being measured at specific times (e.g., morning or evening). Bring any medications you’re taking to your appointment.
During the Test
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch or discomfort, but it usually takes only a few minutes. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results are compared to standard ranges for your age, sex, and health status. High cortisol levels may indicate overproduction by your adrenal glands, while low levels could suggest adrenal insufficiency or other issues.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels help diagnose conditions like Cushing’s syndrome (excess cortisol) or Addison’s disease (insufficient cortisol). It’s also used to assess stress responses, evaluate pituitary-adrenal axis function, and monitor treatments for hormonal disorders.
Short name
Free Cortisol
Frequently asked questions
What causes abnormal cortisol levels?
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