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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, in your blood. Free cortisol is the active, unbound portion that circulates freely in your bloodstream and is available to bind to receptors in your body.

Quick summary

["Free cortisol helps regulate metabolism, immune response, and stress reactions—your doctor may check this test to assess adrenal function or hormone balance."]

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

Key facts at a glance

LOINC
59153-7
Short code
Cortis 5h p chal SerPl-sCnc
Synonyms
Cortis 5h 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 Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like unexplained weight changes, fatigue, mood swings, or signs of hormonal imbalances. It could also be part of an evaluation for conditions like Cushing’s syndrome, adrenal insufficiency, or other endocrine disorders.

What to Expect Before the Test

No special preparation is needed, but if you’re taking medications (like steroids) or have recent stress, your results may be affected. Avoid caffeine or alcohol for 24 hours before testing if instructed by your doctor.

How the Test Works

A blood sample is drawn from a vein in your arm. The lab then measures the free cortisol concentration using a sensitive immunoassay method to detect its presence in your serum.

What the Results Mean

Results help determine whether your cortisol levels are too high (hypercortisolemia) or too low (hypocortisolemia). Abnormal levels may indicate conditions requiring further evaluation, such as hormonal disorders or medication side effects.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What causes cortisol levels to be tested?
Cortisol testing is often done if you have symptoms like persistent fatigue, weight changes, high blood pressure, or unexplained muscle weakness. It may also be part of a broader evaluation for conditions like Cushing’s syndrome, Addison’s disease, or stress-related hormone imbalances.
How long does it take to get the results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
Can diet or stress affect cortisol levels?
Yes, diet (especially caffeine, alcohol, or high-sugar foods) and stress can temporarily alter cortisol levels. If your test is sensitive to these factors, your doctor may provide specific instructions to minimize interference.
  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