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Cortisol, Serum (Free)

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 and metabolism.

Quick summary

["Free cortisol helps assess adrenal function and potential adrenal insufficiency or excess production."]

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

Key facts at a glance

LOINC
50423-3
Short code
Cortis 40M p 100 ug CRH IV SerPl-mCnc
Synonyms
Cortis 40M p 100 ug 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 Is This Test Done?

Your healthcare provider may order this test to evaluate conditions like Cushing’s syndrome (overproduction of cortisol), adrenal insufficiency (underproduction), or to monitor treatment for hormone-related disorders. It can also help diagnose issues affecting cortisol metabolism or stress responses.

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 being measured at specific times (e.g., morning or evening). Bring any medications or supplements you’re taking to your appointment.

What Happens During the Test?

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

What Are Normal Results?

Results are not provided as a single range since cortisol levels vary by time of day, health status, and individual factors. Your results will be interpreted by your provider in relation to your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated free cortisol levels may indicate Cushing’s syndrome, hyperadrenalism, or inappropriate cortisol secretion. Low levels could signal adrenal insufficiency, pituitary disorders, or medications affecting cortisol metabolism. Repeated testing may be needed to confirm or monitor these conditions over time.

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 production), adrenal insufficiency (due to insufficient cortisol), or medications (e.g., steroids). Stress, certain medications, or genetic factors may also influence results.
How often will I need this test?
Your provider will determine the frequency based on your symptoms, diagnosis, or treatment plan. Some patients may need this test once, while others may require follow-up testing every few months or years.
Can I take anything before the blood draw?
If fasting is required, avoid eating or drinking (except water) for 8–12 hours before the test. If fasting isn’t needed, follow any specific instructions your provider gives you, such as stopping certain medications temporarily.
  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