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Cortisol, Free, Serum

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

This test measures the amount of free (unbound) cortisol in your blood. Cortisol is a hormone produced by your adrenal glands that helps regulate metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol levels help assess adrenal gland function and potential adrenal insufficiency or Cushing’s syndrome."]

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

Key facts at a glance

LOINC
1415-9
Short code
Cortis 30M p 1 ug/kg CRH IV SerPl-mCnc
Synonyms
Cortis 30M p 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 This Test Is Done

Your healthcare provider may order a free cortisol test to diagnose or monitor conditions like adrenal insufficiency (Addison’s disease), Cushing’s syndrome, or to evaluate symptoms of abnormal hormone levels, such as fatigue, weight changes, or unusual mood swings.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8 hours before the test if instructed by your provider. Bring any medications you’re currently taking, as they can affect results.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. 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 specific to your age, sex, and overall health. Abnormally high or low levels may indicate underlying conditions requiring further medical evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Cortisol plays a critical role in managing stress, immune function, and metabolism. Abnormal free cortisol levels can signal conditions like adrenal gland disorders, hormonal imbalances, or chronic stress responses that may need medical intervention.

Short name

Free Cortisol

Frequently asked questions

What causes abnormal cortisol levels?
Abnormal cortisol levels can result from conditions like primary adrenal insufficiency (e.g., Addison’s disease), Cushing’s syndrome (excess cortisol), or secondary adrenal insufficiency due to pituitary hormone imbalances. Chronic stress, certain medications, or tumors affecting the adrenal glands can also influence results.
How long does it take to get results?
Test results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you during a follow-up visit.
Can diet or medications affect cortisol levels?
Yes, certain foods, caffeine, and medications (e.g., steroids, beta-blockers) can temporarily alter cortisol levels. If you’re on long-term medications, inform your provider before the test to ensure accurate results.
  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