Point in view:
Substance A reduces blood glucose
Substance B reduces blood glucose
Substance A and B combined produce net increase in blood glucose (perhaps due to interference or some negative synergistic effect).
I'm just wondering about this as I'm now taking several substances to reduce blood glucose levels (cinnamon, apple cider vinegar, etc etc etc). On the other hand I also practice some habits that may increase them (I oftentimes need caffeine in order to stay up late in order to finish school assignments). So...