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Cortisol, Free (Serum/Plasma)

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 function and detect conditions like Cushing’s syndrome or adrenal insufficiency."]

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

Key facts at a glance

LOINC
107609-0
Short code
Synth Opioids Ur Ql
Synonyms
Synth Opioids Ur Ql
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order a free cortisol test to diagnose or monitor conditions affecting your adrenal glands, such as Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol). It can also help evaluate stress responses or hormone imbalances.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if timing is critical for accurate results. Avoid caffeine or alcohol for 24 hours before testing.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a slight sting, but the procedure usually takes less than a minute. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. High levels may indicate overproduction of cortisol, while low levels may suggest adrenal gland dysfunction. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What causes abnormal cortisol levels?
Abnormal cortisol levels can result from conditions like Cushing’s syndrome (due to excess cortisol from tumors or medications), Addison’s disease (due to adrenal gland failure), or stress-related fluctuations. Other factors, such as certain medications (e.g., steroids) or pituitary disorders, may also affect results.
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 contact you once results are ready, usually within a few days of receiving them.
Can lifestyle changes affect cortisol test results?
Yes, lifestyle factors like caffeine, alcohol, or stress can temporarily alter cortisol levels. For best accuracy, follow your doctor’s instructions regarding fasting, timing, and avoiding substances that may interfere with the test.
  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