Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of the hormone cortisol, in your blood. Cortisol is a steroid hormone produced by your adrenal glands and plays a key role in managing stress, immune response, and metabolism.
["Understanding your free cortisol levels helps assess adrenal function and potential stress-related conditions."]
Key facts at a glance
- LOINC
- 1446-4
- Short code
- Cortis pre 3 g MTP PO ON SerPl-mCnc
- Synonyms
- Cortis pre 3 g MTP PO ON SerPl-mCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 8
- Ref high
- 61
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82977
- 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 healthcare provider may order this test to evaluate adrenal gland function, diagnose conditions like Cushing’s syndrome or Addison’s disease, or check for issues related to cortisol imbalance, especially if you have symptoms such as fatigue, weight changes, or unusual mood swings.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have fasting instructions depending on your specific test order, but generally, you can eat and drink normally unless directed otherwise. Bring any medications you’re taking to your appointment.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. The process is quick and typically causes only mild discomfort. You may feel a slight pinch or pressure during the needle insertion.
What Are Possible Results?
Results are interpreted by your healthcare provider based on your medical history and symptoms. Abnormal results may indicate conditions affecting cortisol production or metabolism, which can be further evaluated with additional tests.
Reference range
Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Free Cortisol
Frequently asked questions
What does a free cortisol test measure?
Why might my doctor order a free cortisol test?
Can I eat or drink before this 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