Cortisol Test: When to Test, What Normal Means, and Why Timing Changes Everything
Cortisol is the body's primary stress hormone, controlling everything from blood sugar regulation to immune function to circadian rhythms. But cortisol levels fluctuate dramatically throughout the day, making a single measurement potentially misleading. A cortisol level of 15 µg/dL might indicate severe adrenal insufficiency at 8 AM or completely normal function at 8 PM. Understanding when and how to test cortisol properly can reveal adrenal dysfunction, chronic stress states, and hormone imbalances that standard testing approaches miss entirely.