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Cortisol, Serum (Free)

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, metabolism, and immune function.

Quick summary

["Free cortisol helps assess adrenal gland health and hormone balance, especially in conditions like Cushing’s syndrome or adrenal insufficiency."]

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

Key facts at a glance

LOINC
77925-6
Short code
Cortis 10M p chal SerPl-sCnc
Synonyms
Cortis 10M 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 This Test Is Done

Your doctor may order a free cortisol test to diagnose or monitor conditions affecting your adrenal glands, such as Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol). It can also help evaluate stress-related hormone imbalances or rule out other causes of fatigue, weight changes, or high blood pressure.

How the Test Works

A blood sample is taken from a vein in your arm. The lab measures the free (non-protein-bound) cortisol level, which reflects your body’s active hormone levels more accurately than total cortisol alone.

What to Expect Before the Test

No special preparation is needed, but avoid high-stress activities or caffeine for 24 hours before testing if your doctor recommends it, as these can temporarily affect cortisol levels.

What the Results Mean

Results are interpreted based on your symptoms, medical history, and other tests. Elevated free cortisol may indicate overproduction by the adrenal glands or pituitary gland, while low levels may suggest adrenal gland dysfunction.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

How often should I get this test?
This test is typically done once or twice if needed for diagnosis or monitoring. Follow your doctor’s recommendations for follow-up based on your specific condition and results.
Can I take anything before the test?
Avoid caffeine, heavy meals, or intense physical activity for 24 hours before testing if advised by your doctor, as these can influence cortisol levels.
What if my results are abnormal?
If your results are abnormal, your doctor may recommend additional tests (like a 24-hour urine cortisol test) or further evaluation to determine the cause and guide treatment.
  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