First off Diabetes is unpredictable, what is safe one day may spike you the next. I do find though if I indulge in a treat that it does make my bgs higher for several days if not more. I think this is because when I eat more than 15 carbs at a time some of it gets stored in my liver and muscles as glycogen. So for several days there is extra glycogen to switch back to glucose whenever my body wants to.