Cortisol, Serum (Free Cortisol)
This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Cortisol is a steroid hormone produced by your adrenal glands and plays a key role in managing stress, immune response, and metabolism.
["Free cortisol helps regulate how your body responds to stress and maintains balance in your body’s systems."]
Key facts at a glance
- LOINC
- 26536-3
- Short code
- Cortis 1h p ACTH SerPl-sCnc
- Synonyms
- Cortis 1h p ACTH SerPl-sCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 60
- 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 order this test to diagnose or monitor conditions related to cortisol levels, such as Cushing’s syndrome (too much cortisol), Addison’s disease (too little cortisol), or to check for adrenal gland issues. It may also be used to evaluate stress responses or assess hormone imbalances before certain treatments.
What to Expect Before the Test
You’ll typically have a simple blood draw from a vein in your arm. No special preparation is usually needed, but your provider may advise against certain foods, medications, or activities for 24 hours before testing if it’s a specific type of cortisol measurement (e.g., 24-hour urine cortisol).
What the Results Mean
Results help determine if your cortisol levels are too high or too low. Abnormal levels can indicate hormonal imbalances or other health conditions. Your provider will interpret the results in the context of your symptoms and medical history.
Common Conditions Linked to Cortisol Levels
High cortisol levels may be linked to conditions like Cushing’s syndrome, which can cause weight gain, fatigue, or high blood pressure. Low cortisol levels, such as in Addison’s disease, may cause weakness, dizziness, or low blood pressure. Regular monitoring is important for managing these conditions.
Reference range
NCBI: ACTH 10-60 pg/mLN/A
Typically collected in the morning (8-10 AM). Inform your provider if taking steroid medications.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Cortisol is essential for managing stress responses, immune function, and metabolism. Chronic stress or imbalances in cortisol can affect energy levels, mood, and overall health. Monitoring free cortisol helps identify whether your body is producing too much or too little, guiding treatment decisions.
Short name
Free Cortisol
Frequently asked questions
What triggers cortisol levels to be checked?
How is the test different from other cortisol tests?
Can diet or medications affect cortisol test results?
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 17, 2026. · Read our editorial policy