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Serum or plasma mass concentration of free cortisol (total cortisol)

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

This test measures the amount of free (unbound) cortisol in your blood, which is the active form of the hormone cortisol.

Quick summary

["Free cortisol helps regulate metabolism, immune response, and stress reactions."]

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

Key facts at a glance

LOINC
56563-0
Short code
GH 7.5h p chal SerPl-mCnc
Synonyms
GH 7.5h p chal SerPl-mCnc
Category
chemistry
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 Is This Test Done?

Your doctor may order this test to evaluate cortisol levels, especially if you have symptoms like unexplained weight changes, fatigue, or signs of either too much (hypercortisolism) or too little (hypocortisolism) cortisol. It can also help diagnose conditions like Cushing’s syndrome or adrenal insufficiency.

What Does the Result Mean?

Results may indicate whether your cortisol levels are too high or too low, helping guide treatment for conditions like adrenal disorders or hormonal imbalances. Interpretation depends on clinical context and other test results.

How Is the Sample Collected?

A blood sample is drawn from a vein, usually in your arm. The sample is processed into serum or plasma within hours to preserve accuracy.

What Preparations Are Needed?

No special preparation is typically required, but you may be asked to avoid certain medications or activities that could affect cortisol levels (e.g., caffeine, stress) for 24 hours before testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Free Cortisol Level

Frequently asked questions

Free cortisol testing is critical for diagnosing conditions like Cushing’s syndrome (excess cortisol) or adrenal insufficiency (low cortisol), which can cause serious health issues if untreated. It helps differentiate between causes of symptoms like weight gain, muscle weakness, or fatigue.
This test may be used alongside other cortisol-related tests (e.g., 24-hour urine cortisol) to confirm or refine diagnosis.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on lab processing times. Your doctor will discuss them with you during a follow-up visit.
Can I take anything for this test?
Avoid caffeine, alcohol, or strenuous exercise for 24 hours before testing, as these can temporarily alter cortisol levels. Follow your doctor’s specific instructions.
  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