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Cortisol, Free (Serum/Plasma)

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

This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Cortisol is involved in regulating stress responses, metabolism, and immune function.

Quick summary

Free cortisol helps assess adrenal gland function and potential hormone imbalances.

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

Key facts at a glance

LOINC
1431-6
Short code
Cortis 5M p 1 ug/kg CRH IV SerPl-mCnc
Synonyms
Cortis 5M p 1 ug/kg CRH IV 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
CPT
86701
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 a free cortisol test to check for conditions like Cushing’s syndrome (too much cortisol) or adrenal insufficiency (too little cortisol). It can also help diagnose issues with the pituitary gland, which controls cortisol production, or evaluate stress-related hormone changes.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The sample is sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications that could affect cortisol levels, such as some steroids or blood pressure medications. If you’re taking them, let your provider know.

What Are Possible Results?

Results are compared to reference ranges specific to your age, sex, and health status. High or low levels may indicate underlying medical conditions that need further evaluation.

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. Abnormal free cortisol levels can signal conditions like adrenal tumors, pituitary disorders, or chronic stress-related hormone imbalances. Your provider will interpret results in the context of your symptoms and medical history.

Short name

Free Cortisol

Frequently asked questions

What causes abnormal cortisol levels?
Abnormal cortisol levels can result from conditions like Cushing’s syndrome (excess cortisol), adrenal insufficiency (low cortisol), or pituitary tumors. Stress, certain medications, or other hormonal imbalances may also affect results.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your provider will discuss the findings with you during your follow-up visit.
Can I eat or drink before this test?
You can eat and drink normally before the test unless instructed otherwise. Avoiding caffeine or alcohol for a few hours before your appointment may help ensure more accurate results.
  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