Cortisol, Serum (Free)
This test measures the amount of free cortisol, a hormone produced by your adrenal glands, in your blood. Free cortisol is the active form that circulates in your bloodstream and 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
- 58829-3
- Short code
- Cortis sp15 SerPl-mCnc
- Synonyms
- Cortis sp15 SerPl-mCnc
- 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 like unexplained fatigue, weight changes, mood swings, or signs of hormonal imbalances. It could also be used to diagnose or monitor conditions such as Cushing’s syndrome, adrenal insufficiency, or other adrenal or pituitary disorders.
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 cortisol levels are measured at specific times (e.g., morning or evening). If you’re taking medications that affect cortisol, let your provider know. Avoid caffeine or alcohol before testing as they can influence results.
What Happens During the Test
A healthcare professional will draw blood from a vein in your arm. The blood sample will be sent to a lab for analysis. The process typically takes a few minutes, and you may feel slight discomfort but no lasting effects.
What the Results Mean
Results are interpreted based on your symptoms, medical history, and timing of the blood draw (e.g., morning vs. evening). Abnormal results may indicate conditions like too much or too little cortisol, which can affect your energy, weight, or stress responses. Your provider will discuss these findings with you.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free cortisol levels help diagnose or evaluate conditions related to the adrenal glands or pituitary gland, such as hypercortisolism (e.g., Cushing’s syndrome) or hypocortisolism (e.g., Addison’s disease). It’s also used to monitor treatment responses in patients on long-term steroid therapy or those with suspected adrenal dysfunction. Consistently high or low levels can signal underlying health concerns that require further medical evaluation.
Short name
Free Cortisol
Frequently asked questions
How often will I need this test?
Can I eat or drink anything before the test?
Will the test affect my daily activities?
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