Cortisol Testing: Stress Hormone Levels and Timing
Cortisol is the body's main stress hormone, produced by the adrenal glands and controlled by the pituitary. Levels normally peak in the early morning and fall through the day, so the collection time is part of the result. A morning blood cortisol is often used to investigate fatigue, low blood pressure, or suspected adrenal insufficiency, while an evening or late-night sample can help evaluate excess cortisol. Walk-in collection makes a timed draw straightforward. This guide explains the patterns and why a single random cortisol is rarely enough.
Key Takeaways
- Cortisol is produced by the adrenal glands and follows a strong daily rhythm.
- Morning levels are highest and evening levels are lowest in a normal pattern.
- A morning cortisol is commonly used to investigate possible adrenal insufficiency.
- Persistently high cortisol may suggest Cushing syndrome and usually needs confirmatory testing.
- A single random cortisol is hard to interpret; collection time must be recorded.
Frequently Asked Questions
When should cortisol be tested?
Morning collection is typical for suspected low cortisol, while late-night or evening collection may be used for suspected excess. Follow your order's timing instructions exactly.
Can stress raise cortisol?
Yes. Acute stress, illness, and sleep disruption can raise cortisol, which is why results are interpreted with symptoms and sometimes repeat testing.
Do I need to fast for a cortisol test?
Fasting is often not required, but timing matters more than fasting. Follow the instructions on your order.
Can I order a cortisol test without a doctor?
Yes. Direct-access lab testing lets you order a morning or timed cortisol test and collect the sample at a walk-in site.
Sources
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