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Cortisol, Serum (Free Cortisol)

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

This test measures the amount of free cortisol, a form of the hormone cortisol, in your blood. Free cortisol is the active, non-protein-bound form that circulates freely in your bloodstream and is important for regulating stress responses and metabolism.

Quick summary

["Free cortisol helps your body respond to stress and maintain normal hormone balance."]

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

Key facts at a glance

LOINC
50442-3
Short code
Cortis 20M p Ins IV SerPl-mCnc
Synonyms
Cortis 20M p Ins 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
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 of either too much cortisol (hypercortisolism) or too little cortisol (hypocortisolism), such as unexplained weight changes, fatigue, mood swings, or unusual thirst. It could also be used to diagnose conditions like Cushing’s syndrome or Addison’s disease, or to monitor treatment for these conditions.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into your arm to draw blood. If you’re taking medications that affect cortisol levels (like steroids), let your provider know before the test.

What the Results Mean

Free cortisol levels can vary based on your time of day, stress levels, and other health factors. Your results will be compared to standard ranges to help identify any imbalances. High levels might suggest conditions like Cushing’s syndrome, while low levels could indicate Addison’s disease or other adrenal issues.

Common Conditions Monitored

This test is often used to diagnose or monitor conditions such as Cushing’s syndrome (excess cortisol), Addison’s disease (adrenal insufficiency), or to check for cortisol-related disorders that affect your body’s stress response.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Free Cortisol

Frequently asked questions

What could cause abnormal cortisol levels?
Abnormal cortisol levels can result from conditions like chronic stress, certain medications (such as steroids), tumors affecting the adrenal glands or pituitary gland, or autoimmune diseases. It can also be influenced by thyroid disorders, kidney problems, or liver disease.
How often should I get this test?
The frequency depends on your medical condition and treatment plan. Your healthcare provider will determine how often you need retesting, whether it’s for diagnosis, monitoring, or managing an existing condition.
Does diet or lifestyle affect cortisol levels?
Yes, diet, stress levels, exercise, and sleep can impact cortisol. Avoiding caffeine, alcohol, and heavy meals before the test may help ensure more accurate results. Stressful activities or events before testing can also temporarily alter cortisol levels.
  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