Cortisol, Free (Serum)
This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Free cortisol is important for regulating stress responses, metabolism, and other bodily functions.
["Free cortisol helps your body manage stress and maintain balance in your hormones."]
Key facts at a glance
- LOINC
- 1430-8
- Short code
- Cortis 56h p 40 ug ACTH IM SerPl-mCnc
- Synonyms
- Cortis 56h p 40 ug ACTH IM SerPl-mCnc
- 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 Is This Test Done?
Your healthcare provider may order a free cortisol test to diagnose or monitor conditions related to abnormal cortisol levels, such as Cushing’s syndrome (too much cortisol) or Addison’s disease (too little cortisol). It can also help assess adrenal gland function or evaluate symptoms like unexplained weight changes, fatigue, or mood swings.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a 24-hour cortisol collection. If testing is done in the morning, you can eat and drink normally. If testing is done at night, fasting may be required.
What Happens During the Test?
A healthcare provider will draw blood from a vein in your arm. You may feel a small pinch, but it usually doesn’t cause discomfort. The blood sample will be sent to a lab for analysis.
What to Expect After the Test
You may experience mild bruising, swelling, or discomfort at the injection site, which typically goes away within a few days. Avoid vigorous activity for 24 hours to prevent excessive bruising.
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 levels can indicate hormonal imbalances. High levels may suggest conditions like Cushing’s syndrome, which can cause weight gain, muscle weakness, or high blood pressure. Low levels may point to Addison’s disease, leading to fatigue, low blood pressure, or darkening of the skin. Chronic stress or certain medications can also affect cortisol levels, so results should be interpreted by a healthcare provider in the context of your overall health.
Short name
Free Cortisol
Frequently asked questions
What does a high or low free cortisol level mean?
How often should I get this test?
Can lifestyle changes 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 17, 2026. · Read our editorial policy