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Cortisol, Free (Serum)

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 metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol helps your body manage stress and maintain balance in key bodily functions."]

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

Key facts at a glance

LOINC
50416-7
Short code
Cortis p 2 mg Dex SerPl-mCnc
Synonyms
Cortis p 2 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 healthcare provider may order a free cortisol test to check for conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or other hormonal imbalances. It can also help diagnose issues with the pituitary gland or adrenal glands that affect 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 provider know before the test.

What Happens During the Test?

A healthcare professional will collect a blood sample from a vein in your arm. The sample will be sent to a lab for analysis. The test typically takes a few minutes, and you may feel slight discomfort or bruising afterward.

What Are the Results?

Results are interpreted based on your medical history, symptoms, and other test results. Elevated or low free cortisol levels may indicate underlying health conditions that need 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?
This test measures the amount of cortisol that is not bound to proteins in your blood, providing a more accurate reflection of your body’s active cortisol levels.
How is the specimen collected?
Blood is drawn from a vein in your arm using a small needle. The sample is then sent to a lab for analysis.
Can I take anything before the test?
No special preparation is required, but inform your provider if you’re taking medications that might affect cortisol levels, such as steroids.
  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