Cortisol, Free (Serum or Plasma)
This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Free cortisol is important for regulating stress responses, metabolism, and other bodily functions.
["Free cortisol helps your body manage stress and maintain balance in your hormones and metabolism."]
Key facts at a glance
- LOINC
- 59804-5
- Short code
- Cortis 1h p chal SerPl-SCDiff
- Synonyms
- Cortis 1h p chal SerPl-SCDiff
- 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 This Test Might Be Ordered
Your healthcare provider may order a free cortisol test to check for conditions like Cushing’s syndrome (too much cortisol), adrenal insufficiency (too little cortisol), or to monitor treatment for hormone-related disorders. It can also help diagnose issues with the pituitary gland or adrenal glands.
What to Expect During the Test
You’ll have a simple blood draw from a vein in your arm. The sample is collected in a tube and sent to a lab for analysis. No special preparation is needed unless instructed otherwise.
Sample Collection and Processing
The test uses either serum (blood without clotting factors) or plasma (blood with clotting factors removed). Free cortisol is separated from bound cortisol to provide an accurate measurement of the active form.
What the Results Mean
Results help determine whether your cortisol levels are too high or too low, which can indicate underlying health issues. Your provider will interpret the results in relation to your symptoms and medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Cortisol plays a key role in the body’s stress response, immune function, and metabolism. Abnormal levels can signal conditions affecting the adrenal glands, pituitary gland, or other hormonal imbalances. Free cortisol testing is critical for diagnosing conditions like Cushing’s disease or Addison’s disease.
Short name
Free Cortisol
Frequently asked questions
What causes a free cortisol test to be recommended?
How long does it take to get the results of a free cortisol test?
Can I eat or drink before a free cortisol blood 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