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Cortisol, Serum (Free Cortisol)

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

This test measures the amount of free cortisol, a form of cortisol found in your blood, which is important for managing stress and regulating hormones.

Quick summary

["Free cortisol helps your body respond to stress and maintain healthy hormone balance."]

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

Key facts at a glance

LOINC
45184-9
Short code
11DC/Cortis SerPl
Synonyms
11DC/Cortis SerPl
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), adrenal insufficiency (too little cortisol), or to evaluate how your body handles stress responses. It can also help diagnose hormonal imbalances or monitor treatment for conditions affecting cortisol levels.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The sample is processed to measure free cortisol levels, which are then analyzed in a lab. Free cortisol is distinct from bound cortisol, so this test focuses specifically on the active, unbound form.

How Is the Test Performed?

The blood sample is collected by a healthcare professional, typically in the morning when cortisol levels are naturally highest. The sample is sent to a lab where it is tested using an immunoassay method to detect free cortisol concentration.

What Are the Results Meaningful For?

Results help determine whether cortisol levels are too high or too low, aiding in the diagnosis and management of hormonal disorders. Elevated levels may indicate conditions like Cushing’s syndrome, while low levels may suggest adrenal insufficiency or other stress-related issues.

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?
A free cortisol test measures the amount of cortisol that is not bound to proteins in your blood, which is the biologically active form of cortisol. This helps doctors assess stress responses and hormone balance more accurately than total cortisol alone.
Why might my doctor recommend a free cortisol test?
Your doctor may recommend this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or signs of hormonal imbalances. It can also be used to monitor conditions like Cushing’s syndrome or adrenal disorders.
How soon will I get my results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
  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