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 bloodstream.
["Free cortisol helps regulate metabolism, immune response, and stress reactions."]
Key facts at a glance
- LOINC
- 15043-3
- Short code
- Cortis Ur-sCnc
- Synonyms
- Cortis Ur-sCnc
- Category
- hormone
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order a free cortisol test to diagnose or monitor conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to evaluate stress-related hormone imbalances. It can also help assess cortisol levels during sleep studies or in cases of suspected pituitary disorders.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if cortisol levels are being measured at specific times of the day. Avoid caffeine or stress-inducing activities for a few hours beforehand if instructed.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch or discomfort, but it typically lasts only a few seconds. The blood sample will be sent to a lab for analysis.
What Are the Results Measured Against?
Results are compared to standard reference ranges for cortisol concentration in serum, which can vary slightly depending on the lab and testing method. These ranges help determine if your cortisol levels are within normal limits or if further evaluation is needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated free cortisol levels may indicate conditions such as Cushing’s syndrome, where the body produces too much cortisol, or certain types of tumors affecting the adrenal glands or pituitary gland. Low cortisol levels can signal adrenal insufficiency, where the body fails to produce enough cortisol to maintain normal function. Monitoring free cortisol helps diagnose these conditions early and guides treatment decisions, such as medication adjustments or surgical interventions.
Short name
Free Cortisol
Frequently asked questions
What does a free cortisol test measure?
Can I eat or drink before the test?
How long does it take to get the results?
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