Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a hormone produced by your adrenal glands, in your blood. Free cortisol is the active form that circulates freely in your serum.
["Free cortisol helps regulate stress responses and metabolism; abnormal levels may signal adrenal gland issues or other health concerns."]
Key facts at a glance
- LOINC
- 12562-5
- Short code
- Cortis sp7 p chal SerPl-mCnc
- Synonyms
- Cortis sp7 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 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 pituitary gland function or rule out certain hormonal disorders.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if timing your cortisol levels around a specific time of day (e.g., morning or evening) is important for your test. Bring any medications you’re currently taking to your appointment.
What Happens During the Test?
A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels accurately.
What Does the Test Result Mean?
Results are compared to reference ranges for free cortisol in serum, which can vary slightly by lab. High levels may indicate overproduction of cortisol, while low levels may suggest adrenal or pituitary problems. Your doctor will interpret results in the context of your symptoms and medical history.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels help identify hormonal imbalances that can cause symptoms like weight changes, fatigue, high blood pressure, or unexplained muscle weakness. For example, elevated cortisol may point to Cushing’s syndrome, while low cortisol could signal Addison’s disease or other adrenal dysfunctions. This test is also used in conjunction with other tests (like 24-hour urine cortisol or ACTH stimulation) for a complete evaluation.
Short name
Free Cortisol
Frequently asked questions
How long does it take to get my test results?
What if my cortisol level is outside the normal range?
Can I take any medications before my 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