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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 stress responses, metabolism, and immune function.

Quick summary

["Free cortisol helps your body manage stress and maintain balance in your body’s systems."]

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

Key facts at a glance

LOINC
1437-3
Short code
Cortis 8h p 500 ug Dex SerPl-mCnc
Synonyms
Cortis 8h p 500 ug 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 diagnose or monitor conditions such as Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to check for cortisol-related issues in people with certain cancers or autoimmune diseases.

What to Expect Before the Test

No special preparation is usually needed, but your doctor may instruct you to avoid certain medications or activities for a few days before the test. Bring any medications you’re taking to your appointment.

How the Test Is Performed

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

What the Results Mean

Results are compared to reference ranges specific to your age, sex, and health status. Abnormally high or low levels may indicate underlying health conditions that require further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Free cortisol levels can provide critical insights into adrenal gland function and stress responses. Elevated levels may suggest conditions like Cushing’s syndrome, while low levels could indicate adrenal insufficiency or other hormonal imbalances. Your doctor will interpret results in the context of your medical history and symptoms.

Short name

Free Cortisol

Frequently asked questions

What causes free cortisol levels to be tested?
Your doctor may recommend this test if you have symptoms like unexplained weight gain, fatigue, high blood pressure, or unusual hair growth, or if you have a known risk for adrenal or pituitary disorders.
How long does it take to get the results of this test?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Follow-up with your doctor to discuss findings.
Can I take my usual medications before this test?
Yes, but inform your doctor or lab technician about all medications you’re taking, as some may affect cortisol levels.
  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