I cannot tell you the number of times when I have thought that I have had low blood sugar, only to test and determine that I have high blood sugar. And over the years you can get so used to either high or low blood sugar that you don't even recognize it anymore. One of the things that they tell you on day 1 of being a diabetic is to not trust your feelings. Trust the glucose tester.

I am a type 1 diabetic and wear a sensor 24/7 that monitors my blood sugar. I realize that this is a specialized case, but for certain things the technology and need already exists and are being used.