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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, a hormone produced by your adrenal glands that helps regulate stress responses, metabolism, and immune function.

Quick summary

["Free cortisol helps assess adrenal gland function and potential hormone imbalances."]

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

Key facts at a glance

LOINC
32313-9
Short code
Cortis 30M p chal SerPl-sCnc
Synonyms
Cortis 30M 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, high blood pressure, or signs of adrenal insufficiency (such as low blood pressure upon standing). It could also be used to evaluate conditions like Cushing’s syndrome, adrenal tumors, or hypercortisolism.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if cortisol levels are measured at specific times (e.g., morning or evening). Bring any medications you’re taking, as they could affect results.

How the Test Is Performed

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

What the Results Mean

Results are compared to standard reference ranges, but individual ranges may vary based on lab methods. High cortisol levels may indicate overproduction by the adrenal glands or pituitary gland, while low levels could suggest adrenal gland dysfunction or other hormonal issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What causes free cortisol levels to be tested?
Free cortisol testing is often ordered 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 suspected hormonal disorders, such as adrenal tumors or pituitary issues.
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 healthcare provider will discuss the findings with you during your follow-up visit.
Can diet or medications affect cortisol levels?
Yes, certain medications (e.g., steroids, beta-blockers) and dietary factors (e.g., caffeine, alcohol) can influence cortisol levels. If you’re on 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