Serum or plasma mass concentration of free cortisol
This test measures the amount of free (unbound) cortisol in your blood, which helps assess your body’s cortisol levels and hormone balance.
["Free cortisol helps diagnose conditions like Cushing’s syndrome or adrenal insufficiency."]
Key facts at a glance
- LOINC
- 56561-4
- Short code
- GH 5.5h p chal SerPl-mCnc
- Synonyms
- GH 5.5h p chal SerPl-mCnc
- Category
- chemistry
- 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 Is Done
Your doctor may order this test if you have symptoms of hormonal imbalances, such as unexplained weight changes, high blood pressure, or unusual fatigue. It may also be used to monitor conditions like Cushing’s syndrome or adrenal gland disorders.
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 cortisol levels are measured at specific times of day. Bring any medications you’re currently taking to your appointment.
How the Test Is Performed
A blood sample is drawn from a vein in your arm by a healthcare professional. The sample is then sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels.
What the Results Mean
Results are compared to reference ranges specific to your age, sex, and health status. High or low free cortisol levels may indicate underlying medical conditions that require further evaluation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol testing is critical for diagnosing conditions such as Cushing’s syndrome (excess cortisol) or adrenal insufficiency (low cortisol). It helps rule out hormonal disorders affecting metabolism, stress response, and immune function. Persistently abnormal results may guide treatment, such as medication adjustments or further diagnostic testing.
Short name
Free Cortisol Level
Frequently asked questions
What does a high free cortisol level mean?
What does a low free cortisol level mean?
Why is free cortisol different from total cortisol?
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