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Cortisol, Serum, Free (Mass Concentration)

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.

Quick summary

["Free cortisol helps regulate metabolism, immune response, and stress reactions."]

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

Key facts at a glance

LOINC
50454-8
Short code
Cortis sp2 SerPl-mCnc
Synonyms
Cortis sp2 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 check for conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to monitor treatment for these conditions. It can also help diagnose pituitary disorders or evaluate stress-related hormone imbalances.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The sample is processed to measure the free (non-protein-bound) cortisol level in your serum.

What to Expect Before the Test

No special preparation is usually needed, but you may be advised to avoid certain medications or activities that could affect cortisol levels, such as caffeine or strenuous exercise, depending on your doctor’s instructions.

What Are Common Causes of Abnormal Results?

High levels may suggest conditions like Cushing’s syndrome, excessive use of steroids, or stress. Low levels could indicate adrenal gland problems, pituitary disorders, or conditions like Addison’s disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Cortisol plays a critical role in managing stress, immune function, and metabolism. Abnormal free cortisol levels can signal underlying hormonal imbalances that require medical evaluation and treatment.

Short name

Free Cortisol

Frequently asked questions

What triggers cortisol testing?
Cortisol testing may be triggered by symptoms like unexplained weight changes, fatigue, high blood pressure, or frequent infections, or if your doctor suspects hormonal imbalances based on medical history or other tests.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on lab processing times and your healthcare provider’s workflow.
Can lifestyle changes affect cortisol levels?
Yes, lifestyle factors like sleep quality, stress levels, diet, and exercise can influence cortisol. Avoiding extreme stress, maintaining a consistent sleep schedule, and managing chronic stress may help stabilize 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