Cortisol (Serum) Overnight Free (Qualitative or Quantitative Screening)
This test measures cortisol levels in your blood after an overnight fast to assess adrenal function and hormone balance.
["Understanding your cortisol levels can help diagnose conditions like adrenal insufficiency or Cushing’s syndrome."]
Key facts at a glance
- LOINC
- 55138-2
- Short code
- Cortis p Dex overnight SerPl-mCnc
- Synonyms
- Cortis p Dex overnight 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 Is Done
Your doctor may order this test if you have symptoms like fatigue, weight changes, or unexplained stress responses. It helps evaluate how well your adrenal glands are producing cortisol, a hormone that regulates stress, metabolism, and immune function.
What to Expect Before the Test
You’ll need to fast (not eat or drink anything except water) for 12 hours before the test. Bring your fasting blood sample in the morning after waking up without caffeine or alcohol.
How the Test Works
A blood sample is taken from a vein in your arm. The test measures cortisol concentration, either qualitatively (yes/no presence) or quantitatively (exact amount). Results help determine if your cortisol levels are too high or too low.
Possible Results and Next Steps
Abnormal results may prompt further testing, such as additional cortisol measurements or imaging studies to identify underlying causes like adrenal tumors or pituitary disorders.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Will I need to prepare for this test at home?
How long will it take to get my results?
Can I take medications before this test?
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