For a normally-functioning metabolism, most of the ways the body interacts with blood glucose is about providing the body with glucose - to help with fending off that pesky lion, or to help out with dealing with an infection, or simply to deal with the process of engaging with deep sleep.
Because we are diabetic, we tend to think that there is only this simple relationship between insulin and food, but it's much more than that.
The kind of reaction that you show is alarming; but the reason for it is actually pretty natural, you need the energy to become well again.