Serum/plasma free cortisol concentration (mass concentration)
This test measures the amount of cortisol that is not bound to proteins in your blood, which helps assess how your body is responding to stress or certain hormone-related conditions.
["Free cortisol levels can indicate stress responses or hormone imbalances."]
Key facts at a glance
- LOINC
- 47762-0
- Short code
- GH 1h p Ins IV SerPl-aCnc
- Synonyms
- GH 1h p Ins IV SerPl-aCnc
- 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 recommend this test if you have symptoms like unexplained weight changes, fatigue, mood swings, or if they suspect conditions like Cushing’s syndrome, adrenal insufficiency, or other hormonal disorders. It may also be used to monitor treatment for conditions affecting cortisol levels.
How the Test Works
Blood is drawn from a vein, and the cortisol that is not attached to proteins (free cortisol) is measured using a sensitive laboratory method to detect very small amounts in your blood.
What to Expect Before the Test
No special preparation is usually needed, but you may be advised to avoid certain medications or activities that could affect cortisol levels, such as caffeine or stress. If you are taking corticosteroids (like prednisone), let your provider know.
What to Expect During the Test
The blood sample is taken from a vein in your arm, similar to other blood tests. You may feel a slight pinch, but it usually doesn’t cause discomfort. The sample is then sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels can provide important clues about how your body regulates stress hormones. High levels may suggest conditions like Cushing’s syndrome, while low levels could indicate adrenal insufficiency or other hormonal imbalances. This test helps guide treatment decisions and monitor ongoing conditions.
Short name
Free Cortisol
Frequently asked questions
What does a free cortisol test measure?
How is the free cortisol test different from a standard cortisol test?
Can stress affect the results of a free cortisol 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