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Cortisol, Free (Serum or 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. Free cortisol is important for regulating stress responses, metabolism, and other bodily functions.

Quick summary

["Free cortisol helps your body manage stress and maintain normal hormone balance."]

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

Key facts at a glance

LOINC
47844-6
Short code
Cortis p 1 mg Dex SerPl-mCnc
Synonyms
Cortis p 1 mg Dex 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 check for conditions like Cushing’s syndrome (a hormonal disorder where your body makes too much cortisol) or adrenal insufficiency (when your adrenal glands don’t produce enough cortisol). It can also help diagnose issues with your pituitary gland, which controls cortisol production.

What to Expect Before the Test

No special preparation is needed for this test. You’ll have a small needle inserted into your arm to draw blood. If you’re taking medications that affect cortisol levels (like steroids), let your doctor know before the test.

What Happens During the Test?

Blood is collected from a vein in your arm. The sample is then sent to a lab for analysis. Free cortisol is measured in the blood plasma or serum, not protein-bound forms.

What Are the Results Mean?

Results are interpreted by your healthcare provider based on your symptoms and medical history. Abnormal levels may indicate hormonal imbalances or other health conditions requiring further evaluation.

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?
It measures the amount of cortisol that is not bound to proteins in your blood, which reflects your body’s active cortisol levels.
How is the test different from a total cortisol test?
A free cortisol test focuses only on the unbound (active) cortisol, while a total cortisol test includes both free and protein-bound cortisol. Free cortisol is often more accurate for diagnosing certain hormonal disorders.
Can stress affect my free cortisol test results?
Yes, stress or recent illness may temporarily alter cortisol levels. Your doctor may recommend testing at a specific time (e.g., morning) or additional testing to account for natural fluctuations.
  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