Skip to content

Cortisol, Free, Serum

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, metabolism, and other bodily functions.

Quick summary

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

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

Key facts at a glance

LOINC
1445-6
Short code
Cortis pre 1 mg Dex SerPl-mCnc
Synonyms
Cortis pre 1 mg Dex 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
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 recommend this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or signs of adrenal insufficiency or hyperfunction (such as Cushing’s syndrome). It may also be used to monitor conditions like Addison’s disease or to evaluate stress-related hormone levels before procedures.

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 blood draw if cortisol levels are being measured at specific times (e.g., morning or evening). Avoid caffeine or alcohol for 24 hours prior if instructed.

How the Test Works

A small sample of your blood is taken from a vein, typically in your arm. The sample is then analyzed in a lab to measure free cortisol levels using a sensitive immunoassay method to detect hormone concentrations accurately.

What the Results Mean

Results help determine if your adrenal glands are producing cortisol at normal or abnormal levels. Elevated or low free cortisol can indicate conditions requiring medical attention, such as hormonal disorders or stress-related issues.

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 adrenal gland disorders (e.g., tumors, infections), pituitary gland issues, chronic stress, or certain medications (e.g., steroids). Symptoms like weight changes, fatigue, or mood swings may signal underlying problems.
How often should I get this test?
Your doctor will determine the frequency based on your symptoms, medical history, and treatment needs. Follow-up tests may be scheduled periodically to monitor changes in cortisol levels.
Can diet or lifestyle affect cortisol test results?
Yes, diet (e.g., caffeine, alcohol), stress, or timing of blood draws (e.g., morning vs. evening) can influence cortisol levels. Follow your provider’s instructions to ensure accurate results.
  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