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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 form that your body uses to regulate stress responses and other vital functions.

Quick summary

["This test helps assess how well your body produces cortisol and whether it’s balanced with other hormones."]

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

Key facts at a glance

LOINC
77936-3
Short code
Cortis 10.5h p chal SerPl-sCnc
Synonyms
Cortis 10.5h 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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of hormonal imbalances, such as excessive fatigue, weight changes, or unusual mood swings. It could also be used to diagnose conditions like Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol).

What to Expect Before the Test

No special preparation is needed for this blood 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 beforehand.

What the Results Mean

The results help determine if your cortisol levels are too high or too low. Abnormal levels may indicate conditions affecting your adrenal glands or pituitary function. Your provider will interpret the results in relation to your symptoms and medical history.

Common Conditions Linked to Cortisol Testing

High cortisol levels might suggest conditions like Cushing’s syndrome, which can cause weight gain, high blood pressure, or muscle weakness. Low cortisol levels could point to Addison’s disease, leading to fatigue, dizziness, or low blood pressure.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Free Cortisol

Frequently asked questions

How often will I need this test?
This test may be repeated based on your symptoms or treatment plan. Your provider will let you know if follow-up testing is needed, such as during monitoring for hormonal disorders or after starting new medications.
Can I eat or drink before this test?
You can eat and drink normally before this test unless instructed otherwise. Cortisol levels can be affected by stress or certain foods, but standard blood tests don’t require fasting unless specified for other tests.
What if I’m stressed before the blood draw?
Stress can temporarily raise cortisol levels. If you’re feeling anxious or have high stress, let your provider know. They may adjust your test timing or interpretation if needed.
  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