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Serum or Plasma Free Cortisol (Quantitative)

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

This test measures the amount of cortisol present in your blood as it circulates freely (not bound to proteins). Cortisol is a hormone produced by your adrenal glands that helps regulate metabolism, immune response, and stress reactions.

Quick summary

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

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

Key facts at a glance

LOINC
73918-5
Short code
JWH-073 Ur Ql Cfm
Synonyms
JWH-073 Ur Ql Cfm
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
confirm
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 healthcare provider may order a free cortisol test to diagnose conditions like Cushing’s syndrome (excess cortisol), adrenal insufficiency (low cortisol), or to evaluate cortisol levels during stress or certain medications. It can also help monitor treatment progress for hormone-related disorders.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications (like steroids) that could affect cortisol levels. If you’re taking them, check with your doctor first. Blood is drawn from a vein, usually in your arm, and the sample is sent to a lab for analysis.

What Happens During the Test

A healthcare professional will clean your arm’s skin, insert a small needle into a vein, and collect blood into a tube. The process usually takes a few minutes. You may feel a brief pinch or slight discomfort, but it’s temporary. The sample is then processed and sent to a lab for cortisol measurement.

What the Results Mean

Results are compared to standard reference ranges, but exact values can vary by lab. High cortisol levels may indicate overproduction by the adrenal glands or other causes like stress or medications. Low levels could signal adrenal gland issues or other health problems. 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 might lead to abnormal cortisol levels?
Abnormally high cortisol levels may be caused by conditions like Cushing’s syndrome (due to tumors or excess hormone production), prolonged stress, certain medications (e.g., steroids), or pituitary disorders. Low cortisol levels can result from adrenal insufficiency (e.g., Addison’s disease), sudden withdrawal from steroids, or severe illness.
How often should this test be repeated?
Your doctor will determine how often to repeat the test based on your symptoms, diagnosis, and treatment plan. If you’re monitoring a condition like Cushing’s syndrome or adrenal insufficiency, follow-up tests may be scheduled every few months to a year, depending on your situation.
Can lifestyle changes affect cortisol levels?
Yes, lifestyle factors like sleep quality, stress levels, diet, and exercise can influence cortisol. Chronic sleep deprivation, poor diet, or excessive stress may temporarily raise cortisol. However, significant lifestyle changes alone won’t replace medical testing, but they can support overall health and may indirectly affect hormone balance.
  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