Skip to content

Cortisol, Serum (Free Cortisol)

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

This test measures the amount of free cortisol, a hormone produced by your adrenal glands, in your blood serum. Free cortisol is the active form of cortisol that circulates in your bloodstream and is important for regulating metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol helps your body manage stress and maintain balance in your body’s systems."]

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

Key facts at a glance

LOINC
25625-5
Short code
Cortis sp7 p chal SerPl-sCnc
Synonyms
Cortis sp7 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 order a free cortisol test to diagnose or monitor conditions such as Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to check for cortisol-related issues in cases of suspected stress, hormonal imbalances, or certain types of tumors.

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 it’s part of a cortisol profile (e.g., 24-hour urine or multiple-timepoint blood samples). If you’re taking medications that affect cortisol levels, let your provider know.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. The blood sample is then sent to a lab for analysis. Free cortisol is measured in the serum portion of the blood.

What the Results Mean

Results are interpreted based on your clinical context, timing of the sample (e.g., morning vs. evening), and any medications you’re taking. Elevated levels may indicate overproduction of cortisol, while low levels may suggest adrenal gland dysfunction. Your provider will discuss these findings with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

Will I need to fast before this test?
Sometimes yes—your provider may ask you to fast for 8–12 hours before drawing blood, especially if this test is part of a cortisol profile. Always follow their instructions to ensure accurate results.
How long will it take to get my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will contact you once they’re ready to discuss them with you.
Can I take my medications before this test?
Yes, but let your provider know if you’re taking any medications that might affect cortisol levels, such as steroids or certain blood pressure medications. They can help adjust your schedule or timing if needed.
  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