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 of cortisol that circulates in your bloodstream and affects various bodily functions.
["Free cortisol helps regulate stress responses and metabolism; abnormal levels may indicate conditions like Cushing’s syndrome or adrenal insufficiency."]
Key facts at a glance
- LOINC
- 58688-3
- Short code
- Cortis sp11 p chal SerPl-mCnc
- Synonyms
- Cortis sp11 p chal 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 diagnose or monitor conditions such as Cushing’s syndrome (excess cortisol production), adrenal gland disorders, or to assess how well your body responds to stress. It can also help evaluate pituitary gland function or rule out other hormonal imbalances.
What to Expect During the Test
A blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The sample is then sent to a lab for analysis. No special preparation is typically needed unless instructed otherwise by your healthcare provider.
Possible Preparations
To ensure accurate results, avoid certain medications (like some steroids) that may affect cortisol levels 24 hours before your test. If you’re taking them, check with your doctor first. Stressful activities or events before the test may also influence results, so try to relax on the day of your appointment.
What the Results Mean
Results are compared to standard reference ranges for free cortisol in serum. High levels may suggest overproduction of cortisol, while low levels could indicate adrenal gland or pituitary issues. Your doctor will interpret the results in the context of your symptoms and medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol is a key hormone in the body’s stress response and metabolism. Elevated levels can point to conditions like Cushing’s syndrome, where the body produces too much cortisol, or adrenal tumors. Low levels may indicate adrenal insufficiency, where the glands don’t produce enough cortisol, or problems with the pituitary gland that regulates cortisol production. Regular monitoring is important for managing these conditions and preventing complications.
Short name
Free Cortisol
Frequently asked questions
How long does it take to get my test results?
Can I eat or drink before this test?
Will I need to take any special steps if I’m pregnant?
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