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 metabolism, immune response, and stress reactions."]
Key facts at a glance
- LOINC
- 1435-7
- Short code
- Cortis 8h p 2 mg Dex SerPl-mCnc
- Synonyms
- Cortis 8h p 2 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 evaluate conditions affecting your adrenal glands, such as Cushing’s syndrome (overproduction of cortisol) or Addison’s disease (underproduction). It can also help diagnose adrenal insufficiency or monitor treatment for hormone-related disorders.
What Does the Test Involve?
A blood sample is taken from a vein, usually in your arm. You may feel a slight pinch or discomfort, but it typically lasts only a few seconds. The sample is sent to a lab for analysis using an immunoassay method to measure free cortisol levels.
What to Expect Before or After the Test
No special preparation is needed, but avoid taking oral steroids (like prednisone) for 24 hours before testing if instructed. After the draw, you can resume normal activities, though you may experience mild bruising or soreness at the site.
How the Results Are Interpreted
Results are compared to reference ranges specific to your age, sex, and health status. Abnormal levels may indicate hormonal imbalances or other underlying conditions that require further medical evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol testing is critical for diagnosing and managing conditions linked to adrenal dysfunction. High levels may signal Cushing’s syndrome, while low levels can point to Addison’s disease or other adrenal disorders. Your doctor will use these results alongside other tests and symptoms to guide diagnosis and treatment plans.
Short name
Free Cortisol
Frequently asked questions
What causes abnormal cortisol levels?
How long does it take to get the results?
Can I eat or drink before this test?
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