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Serum or plasma concentration of free cortisol

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

This test measures the amount of cortisol (a natural steroid hormone) that is not bound to proteins in your blood, helping assess cortisol levels in your body.

Quick summary

["This test helps diagnose conditions related to abnormal cortisol production or metabolism."]

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

Key facts at a glance

LOINC
50377-1
Short code
vWF CBA Act/Nor PPP IA
Synonyms
vWF CBA Act/Nor PPP IA
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 symptoms like unexplained weight changes, fatigue, mood swings, or signs of hormonal imbalances. It’s also used in diagnosing conditions such as Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol).

What to Expect Before the Test

No special preparation is needed unless instructed. If you’re taking medications that affect cortisol levels (like steroids), your provider may ask you to stop them temporarily or adjust timing. Avoiding caffeine or alcohol for 24 hours before the test can help ensure accurate results.

During the Test

A blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The sample is sent to a lab for analysis.

What the Results Mean

Results are compared to standard ranges for your age and sex. Abnormally high or low levels may indicate underlying health issues that require further medical evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

How long does it take to get my results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will contact you once they have the results.
Can I eat or drink before this test?
You can eat and drink normally unless your provider specifies otherwise. Avoiding caffeine or alcohol for 24 hours before the test may improve accuracy.
Will this test be done at home?
No, this test requires a blood sample taken at a healthcare provider’s office, clinic, or lab. Your provider will schedule the appointment for you.
  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