Cortisol, Serum (Free Cortisol)
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 processes like stress response, metabolism, and immune function.
["Your doctor may order this test to check for conditions affecting cortisol levels, such as adrenal gland issues or Cushing’s syndrome."]
Key facts at a glance
- LOINC
- 24391-5
- Short code
- Cortis 1h p 250 ug ACTH IM SerPl-sCnc
- Synonyms
- Cortis 1h p 250 ug ACTH IM 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 Is Done
Your doctor may recommend a free cortisol test if they suspect an imbalance in your body’s stress response system. This could happen if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or unusual mood swings. It might also be part of a broader evaluation for conditions like adrenal insufficiency (Addison’s disease) or Cushing’s syndrome.
What to Expect Before the Test
No special preparation is needed for this test. You’ll have a small needle inserted into your arm to draw blood. It usually takes a few minutes, and you may feel a brief pinch. If you’re taking medications that affect cortisol levels, like steroids, let your doctor know.
What the Results Mean
Free cortisol levels can vary based on your time of day and overall health. Your doctor will compare your results to what’s typical for your age and health status. Abnormally high or low levels may indicate underlying health concerns that need further investigation.
Common Conditions Linked to Cortisol Imbalances
High cortisol levels might be linked to conditions like Cushing’s syndrome (caused by too much cortisol production) or chronic stress. Low cortisol levels could suggest adrenal insufficiency (like Addison’s disease) or other hormonal imbalances.
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.
Free cortisol testing is important because cortisol plays a key role in managing stress, immune function, and metabolism. Abnormal levels can affect how your body responds to stress, influence blood pressure, and impact energy levels. Your doctor may use these results to guide treatment, such as adjusting medications or identifying underlying causes of symptoms.
Short name
Free Cortisol
Frequently asked questions
What triggers cortisol levels to change?
How long does it take to get results?
Can I eat or drink before the blood draw?
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