Cortisol, Free (Serum or Plasma)
This test measures the amount of free cortisol, a hormone produced by your adrenal glands that helps regulate stress responses, metabolism, and other bodily functions.
["Free cortisol helps assess adrenal gland function and potential stress-related hormone imbalances."]
Key facts at a glance
- LOINC
- 1441-5
- Short code
- Cortis 9h p 3 g MTP PO ON SerPl-mCnc
- Synonyms
- Cortis 9h p 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 diagnose or monitor conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to evaluate how your body responds to stress or medications that affect cortisol levels.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a 24-hour urine collection. For serum/plasma samples, you’ll typically have a small needle inserted into your arm to draw blood.
What Happens During the Test?
Blood is drawn from a vein in your arm, and the sample is sent to a lab for analysis. Free cortisol is separated from protein-bound cortisol to provide an accurate measure of the active hormone.
What Are Possible Results?
Results are interpreted by your healthcare provider based on your symptoms, medical history, and other test results. Abnormal levels may indicate conditions affecting cortisol production or metabolism.
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.
Clinical Significance: Cortisol plays a critical role in managing stress, immune response, and metabolism. Low cortisol levels may signal adrenal insufficiency, while high levels could suggest conditions like Cushing’s syndrome or inappropriate cortisol secretion. This test helps diagnose or guide treatment for these conditions by providing precise measurements of free cortisol in your bloodstream.
Short name
Free Cortisol
Frequently asked questions
Why might my doctor recommend this test?
How long will I need to wait for results?
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