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Cortisol, Serum (Free Cortisol)

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

This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. It helps assess your body’s cortisol levels, which are important for managing stress, immune function, and metabolism.

Quick summary

Free cortisol levels can help diagnose 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
93482-8
Short code
Cortis 1M pre 1 ug/kg CRH IV SerPl-mCnc
Synonyms
Cortis 1M pre 1 ug/kg CRH IV 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
CPT
86701
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms of hormonal imbalances, such as unexplained weight changes, fatigue, high blood pressure, or unusual mood swings. It may also be used to monitor conditions like Cushing’s syndrome or adrenal disorders.

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 test if cortisol timing is critical. Bring any medications you’re taking to your appointment.

How the Test Is Performed

A blood sample is drawn from a vein in your arm. The sample is sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels.

What the Results Mean

Results are compared to reference ranges for your age and health status. Abnormally high or low levels may indicate conditions requiring further medical evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Cortisol is a critical hormone produced by the adrenal glands, regulating stress responses, immune function, and metabolism. Free cortisol (not protein-bound) is often measured to avoid interference from binding proteins. Abnormal results may signal adrenal disorders, Cushing’s syndrome, or other endocrine conditions.

Short name

Free Cortisol

Frequently asked questions

What causes free cortisol levels to be tested?
Free cortisol testing is often done to investigate symptoms like weight gain, muscle weakness, fatigue, or unexplained high blood pressure. It may also be part of diagnosing or monitoring conditions such as Cushing’s disease or adrenal insufficiency.
How long does it take to get the results of this test?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you during your follow-up visit.
Can I take anything before or after the blood draw?
Avoid caffeine or alcohol for 24 hours before the test, as they can affect cortisol levels. If you’re taking medications, ask your provider whether to stop temporarily or adjust timing.
  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