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Cortisol, Free (Serum)

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

This test measures the amount of free (unbound) cortisol in your blood. Cortisol is a hormone produced by your adrenal glands that helps regulate metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol helps doctors assess adrenal function and potential hormone imbalances."]

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

Key facts at a glance

LOINC
48001-2
Short code
Cyto loc ID
Synonyms
Cyto loc ID
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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 doctor may recommend this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or signs of Cushing’s syndrome (such as rounded face or excessive hair growth). It could also be used to evaluate adrenal insufficiency or monitor conditions like Addison’s disease or hypercortisolism.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is then analyzed in a lab to measure the free cortisol levels, which are separated from other proteins in the blood to ensure accurate results.

What to Expect Before the Test

No special preparation is usually needed, but if your doctor has instructions (e.g., fasting or avoiding certain medications), follow them carefully. Stress or certain medications can affect cortisol levels, so inform your doctor about any recent changes in your routine.

What the Results Mean

Results are compared to reference ranges for healthy individuals. Elevated levels may suggest conditions like Cushing’s syndrome, while low levels could indicate adrenal gland problems or other hormonal disorders. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What are the normal ranges for cortisol?
Normal ranges can vary slightly between labs, but free cortisol levels are typically measured in nanograms per deciliter (ng/dL). Your doctor will provide specific guidance based on your test results and clinical picture. Free cortisol is particularly useful because it reflects active hormone levels that can cross cell membranes, unlike bound cortisol.
How often should I get this test?
The frequency depends on your health condition and doctor’s recommendations. Some patients may need this test once, while others with chronic conditions may require periodic monitoring. Follow your healthcare provider’s advice for scheduling.
Can lifestyle changes affect cortisol levels?
Yes, stress, sleep patterns, exercise, and diet can influence cortisol levels. Avoiding extreme stress, maintaining a regular sleep schedule, and managing chronic stress may help stabilize hormone levels. Always discuss lifestyle adjustments with your doctor before making changes.
  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