Unlike the ACTH stimulation test, a blood cortisol serum test is very accurate in determining a one-time cortisol level.

Then why do I not recommend this form of testing when it comes to  diagnosing adrenal fatigue?

Like most adrenal fatigue testing methods, the blood serum cortisol test is a snapshot. You cannot establish a “cortisol curve” (your cortisol fluctuation throughout the day) unless you have your blood drew four times throughout the day (most laboratories will not perform this for you.)  In diagnosing adrenal fatigue determining ones, “cortisol curve” is one of the most important aspects of determining severity and protocols going forward. ^{1 2}

Your cortisol can be normal in the morning, but this does not necessarily mean that it will be normal in the afternoon or night. Most blood is drawn in the morning, and depending on what stage adrenal fatigue you are in you can have normal levels first thing the morning. Just because your cortisol is normal in the morning, you can still have elevated levels throughout the day that would not be shown by a single blood cortisol serum test. ^{3 4}

Even though your blood cortisol may appear diagnostically in range, you still want to be the best area within the diagnostic range if you use this testing method.

Blood Cortisol Serum Test Reference Guide ^{5 6}

• 8 am – You are looking for your results to be near the top of the range.
• Noon – You are looking for your results to be in the upper fourth.
• 5 pm – You are looking for your results to be in the middle of the range.
• 11 pm – You are looking for your results to bellow the middle of the range.

Most laboratories use different testing reference ranges. The different reference ranges is why I did not list the actual numbers your results should be. Your position on the different parts of the range depending on the time of day is what matters the most.

My next blog post in the series will be on 24-hour urine collection and medication tests used for the diagnosing of adrenal issues.