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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 balance in your hormones and metabolism."]

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

Key facts at a glance

LOINC
53346-3
Short code
Cortis DBS-sCnc
Synonyms
Cortis DBS-sCnc
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 (too much cortisol) or adrenal insufficiency (too little cortisol). It can also help diagnose issues related to the pituitary gland or adrenal glands, which produce cortisol.

What Does the Test Involve?

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

What to Expect Before the Test

No special preparation is needed for this test. However, if you are taking medications that affect cortisol levels, your doctor may ask you to stop them temporarily or adjust your dosage beforehand.

What to Expect During the Test

You will lie down or sit comfortably while a healthcare provider inserts a small needle into your arm. A small amount of blood will be drawn into a test tube. The process usually takes a few minutes and may cause a slight pinch or discomfort.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

How is this test different from total cortisol?
Unlike total cortisol, which includes both free and bound cortisol, free cortisol measures only the portion of cortisol that is not attached to proteins and is biologically active. This distinction is important for accurate diagnosis of hormonal disorders.
Does stress affect the results of this test?
Yes, stress can temporarily increase cortisol levels. If your test is scheduled during a stressful period, your doctor may recommend retesting after a few days to get a more accurate reading.
Can I eat or drink anything before the test?
You can eat and drink normally before the test unless your doctor advises otherwise. Avoiding caffeine or alcohol for a few hours before the test may help ensure more consistent 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