As far as I know, the only way for a diabetic to go too low (lower that 4 mmol/L) is if they are taking oral medications that stimulate insulin production, or taking insulin directly.

Otherwise, what you may be experiencing is a drop in blood sugar, from a level too high to a lower one. It is very common for a diabetic who is getting healthier to feel awful. IOW, healthy blood sugars can feel quite bad after being at too high for too long.

I'd hate to see anyone eating to get their blood sugars up to an unhealthy number.