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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, a hormone produced by your adrenal glands that helps regulate stress responses and metabolism.

Quick summary

["Free cortisol helps assess adrenal function and potential adrenal disorders."]

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

Key facts at a glance

LOINC
16674-4
Short code
Cortis 70M p chal SerPl-mCnc
Synonyms
Cortis 70M p chal 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, high blood pressure, or signs of hormonal imbalances. It could also be used to diagnose conditions like Cushing’s syndrome, adrenal insufficiency, or other adrenal-related disorders.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, which usually takes a few minutes. If you’re taking medications that affect cortisol levels, let your provider know.

What the Results Mean

Results are interpreted based on your symptoms and medical history. Elevated levels might suggest conditions like Cushing’s syndrome, while low levels could indicate adrenal insufficiency or other issues. Your provider will discuss findings with you.

Common Conditions This Test Helps Diagnose

This test is often used to diagnose or monitor conditions like Cushing’s disease (overproduction of cortisol), adrenal insufficiency (underproduction), or to evaluate stress responses in certain medical situations.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Cortisol plays a vital role in managing stress, immune response, and metabolism. Abnormal levels can signal underlying health issues that require medical attention.

Short name

Free Cortisol

Frequently asked questions

What causes cortisol levels to be tested?
Cortisol levels may be checked if you have symptoms like persistent fatigue, weight changes, high blood pressure, or if your doctor suspects adrenal gland problems, such as Cushing’s syndrome or Addison’s disease.
How is cortisol measured in this test?
This test measures free cortisol in your blood using a sensitive immunoassay method. Free cortisol is the active, unbound form that circulates in your bloodstream and is easier to interpret than total cortisol levels.
Can diet or medications affect cortisol test results?
Certain medications (like steroids) or dietary factors (e.g., caffeine) can influence cortisol levels. Always inform your healthcare provider about all medications, supplements, or recent changes in diet before testing.
  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