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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, in your blood. Cortisol is involved in regulating metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol levels help assess adrenal function and potential stress-related or hormonal imbalances."]

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

Key facts at a glance

LOINC
50459-7
Short code
Cortis sp7 SerPl-mCnc
Synonyms
Cortis sp7 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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like unexplained weight changes, fatigue, mood swings, or signs of adrenal insufficiency or excess cortisol production. It could also be part of evaluating conditions like Cushing’s syndrome, adrenal tumors, or pituitary disorders.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to avoid certain medications or supplements that could affect results. If you’re taking corticosteroids (like prednisone), your provider may advise timing around the test.

During the Test

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

What the Results Mean

Results help determine if your cortisol levels are too high or too low, which can indicate underlying health issues. Your provider will interpret the results in relation to your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Serum Cortisol

Frequently asked questions

What causes cortisol levels to be tested?
Cortisol levels may be checked if you have symptoms like persistent fatigue, unexplained weight changes, high blood pressure, or signs of hyper- or hypocortisolism. It’s also used to evaluate suspected adrenal or pituitary disorders, Cushing’s syndrome, or adrenal insufficiency.
How is cortisol tested?
A simple blood draw is used to measure free cortisol. The test looks specifically at the unbound (free) form of cortisol, which is the active form that circulates in your bloodstream.
Can diet or medications affect cortisol test results?
Yes, certain medications (like corticosteroids) or supplements can influence cortisol levels. Your provider may ask you to avoid these or adjust timing around the test to get accurate results.
  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