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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 the hormone cortisol, in your blood. Free cortisol is the active, unbound portion that circulates freely in your serum.

Quick summary

["Free cortisol helps regulate stress responses and metabolism."]

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

Key facts at a glance

LOINC
77928-0
Short code
Cortis 75M p chal SerPl-sCnc
Synonyms
Cortis 75M p chal SerPl-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 evaluate conditions affecting your adrenal glands, such as Cushing’s syndrome (overproduction of cortisol) or Addison’s disease (underproduction of cortisol). It can also help diagnose adrenal insufficiency or assess stress-related hormone imbalances.

What to Expect During the Test

A blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually takes only a few minutes. No special preparation is needed unless instructed otherwise by your healthcare provider.

How the Results Are Interpreted

Results are compared to standard reference ranges for free cortisol in serum. Abnormal levels may indicate hormonal imbalances or underlying medical conditions requiring further evaluation.

Common Conditions Linked to Free Cortisol Levels

High cortisol levels might suggest conditions like Cushing’s syndrome, prolonged stress, or certain medications. Low cortisol levels could indicate adrenal gland dysfunction, such as Addison’s disease, or other endocrine disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What does a high or low free cortisol level mean?
A high free cortisol level may signal conditions like Cushing’s syndrome, excessive stress, or certain medications. A low level could indicate adrenal insufficiency or other hormonal imbalances. Your doctor will interpret results in the context of your symptoms and medical history.
How often should I get this test?
The frequency depends on your medical condition and treatment plan. If you have an ongoing hormonal disorder, your doctor may recommend periodic testing to monitor changes. Follow-up may also be needed if symptoms persist or worsen.
Can lifestyle changes affect free cortisol levels?
Yes, stress, diet, sleep, and exercise can influence cortisol levels. Reducing stress, maintaining a balanced diet, and ensuring adequate sleep may help support healthy cortisol regulation. Always discuss lifestyle adjustments with your healthcare provider before making changes, especially if you have a diagnosed condition.
  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