Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of cortisol (a natural steroid hormone) found in your blood. Free cortisol is not bound to proteins and is available to affect your body’s functions.
["Free cortisol levels help assess your body’s stress response and adrenal gland function."]
Key facts at a glance
- LOINC
- 24392-3
- Short code
- Cortis pre 1 mg Dex SerPl-sCnc
- Synonyms
- Cortis pre 1 mg Dex 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 Is Done
Your healthcare provider may order a free cortisol test to diagnose or monitor conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or to check for stress-related hormone imbalances. It can also be used in cases of suspected pituitary disorders or to evaluate long-term cortisol exposure.
What to Expect Before the Test
No special preparation is typically needed, but you may be asked to avoid certain medications (like steroids) that could affect cortisol levels. If you’re taking them, your provider will advise you. You’ll usually have blood drawn from a vein in your arm.
What Happens During the Test
A healthcare professional will insert a small needle into your arm to draw blood. You may feel a slight pinch, but it usually takes only a few minutes. The blood sample is then sent to a lab for analysis.
What the Results Mean
Results are compared to standard reference ranges for free cortisol in serum. Abnormally high or low levels may indicate underlying health conditions that need further evaluation, such as hormone imbalances or stress-related disorders.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels are critical for diagnosing conditions affecting the adrenal-pituitary axis, such as Cushing’s disease (due to excess cortisol from the pituitary) or Addison’s disease (due to adrenal gland failure). Elevated cortisol can also signal chronic stress or certain tumors, while low levels may indicate adrenal insufficiency or other endocrine disorders. Your provider will interpret results in the context of your symptoms and medical history.
Short name
Free Cortisol
Frequently asked questions
What causes abnormal cortisol levels?
How long does it take to get results?
Can diet or exercise affect cortisol levels?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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