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Serum or plasma concentration of free cortisol

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of free (unbound) cortisol in your blood, which helps assess adrenal function and hormone balance.

Quick summary

["Free cortisol levels can indicate adrenal gland health or potential hormone imbalances."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
36297-0
Short code
XR Face 3V
Synonyms
XR Face 3V
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
CPT
86430
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 conditions like Cushing’s syndrome (excess cortisol), adrenal insufficiency, or to monitor cortisol levels in people with pituitary disorders or other hormonal issues.

What Does the Result Mean?

Results may be compared to your baseline or to reference ranges for your age and health status. Abnormal levels can signal whether your adrenal glands are producing too much or too little cortisol.

Common Conditions Monitored

This test is often used to diagnose or monitor conditions such as adrenal tumors, pituitary tumors, or chronic stress-related cortisol changes.

Sample Collection and Preparation

A blood sample is drawn, typically in the morning when cortisol levels are highest. The sample is processed into serum or plasma for testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

Free cortisol helps distinguish between primary adrenal disorders (e.g., Cushing’s syndrome) and secondary causes (e.g., pituitary issues), as cortisol levels behave differently in each case.
Free cortisol testing is important because cortisol is a key stress hormone, and its regulation is critical for metabolism, immune function, and mood.
How is the test performed?
The test uses a blood sample collected in the morning, often via a simple venipuncture. The sample is analyzed using an immunoassay method to measure unbound cortisol levels accurately.
What if my cortisol levels are abnormal?
If your results are outside expected ranges, your provider may recommend further testing, such as a 24-hour urine cortisol test or additional hormone checks to pinpoint the cause.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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