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Serum or plasma concentration of free cortisol

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

This test measures the amount of free (unbound) cortisol in your blood, which helps assess your body’s cortisol levels and hormone balance.

Quick summary

["Free cortisol levels can indicate adrenal function and potential hormone imbalances."]

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

Key facts at a glance

LOINC
34589-2
Short code
vWF Cp PPP Ql
Synonyms
vWF Cp PPP Ql
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
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 Cushing’s syndrome (e.g., rounded face, excessive hair growth). It may also be used to monitor conditions like adrenal insufficiency or to check for cortisol-related disorders before or after treatments like steroid therapy.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the draw if cortisol is measured at certain times of day. If you’re taking medications that affect cortisol, let your provider know. Avoid caffeine or alcohol for a few hours before testing.

What Happens During the Test

A blood sample will be taken from a vein in your arm by a healthcare professional. You may feel a slight pinch, but it’s generally quick and not painful. The sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to reference ranges for your age, sex, and health status. Abnormally high or low levels may signal conditions like Cushing’s disease, adrenal tumors, or other hormonal imbalances. Your provider will discuss these findings with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What does a free cortisol test measure?
It measures the amount of cortisol that is not bound to proteins in your blood, providing a more accurate picture of your body’s active cortisol levels compared to total cortisol.
Can I eat or drink before this test?
Generally, fasting is not required unless your provider specifies timing for cortisol measurement (e.g., early morning or late evening). Avoid caffeine or alcohol for a few hours before testing to ensure accurate results.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to discuss the findings.
  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