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Cortisol, Serum (Free)

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

This test measures the amount of free cortisol, a naturally occurring hormone produced by your adrenal glands. It helps assess adrenal function and potential conditions like Cushing’s syndrome or adrenal insufficiency.

Quick summary

["Free cortisol levels can reveal hormonal imbalances affecting stress response and metabolism."]

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

Key facts at a glance

LOINC
58689-1
Short code
Cortis sp11 p chal SerPl-sCnc
Synonyms
Cortis sp11 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 Is This Test Done?

Your doctor may order this test to diagnose or monitor conditions related to abnormal cortisol production, such as Cushing’s disease (overproduction) or Addison’s disease (underproduction). It can also help evaluate stress responses or rule out hormonal disorders like adrenal tumors.

What to Expect Before the Test

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

How the Test Works

A blood sample is taken from a vein in your arm. The serum (liquid part of blood) is then analyzed to measure free cortisol levels using a sensitive laboratory method.

What the Results Mean

Results are compared to reference ranges for your age and health status. Abnormally high or low levels may signal underlying conditions requiring further evaluation, such as imaging or additional hormone tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Cortisol plays a key role in regulating metabolism, immune response, and stress reactions. Persistently elevated or low cortisol can cause fatigue, weight changes, or other symptoms, prompting further medical evaluation to identify causes like tumors, medications, or chronic stress.

Short name

Free Cortisol

Frequently asked questions

What causes abnormal cortisol levels?
Conditions such as Cushing’s syndrome (due to excess cortisol from tumors or overactive pituitary), Addison’s disease (adrenal insufficiency), or prolonged stress (e.g., chronic illness, depression) may lead to abnormal results. Medications (e.g., steroids) or certain medications (e.g., birth control) can also affect cortisol levels.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Your doctor will discuss findings during your follow-up visit.
Can diet or medications affect cortisol test results?
Yes—fasting before testing may be required, and certain medications (e.g., steroids, birth control pills) can influence cortisol levels. Always inform your healthcare provider about all medications or supplements you’re taking.
  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