For me I have found out that the higher my bg goes the more I have to inject to get it down , if my bg goes up to 10 I will need 4 units to get it back down if it goes up to 14 it will be more like 10 units extra , if I make a mistake with the timing of my jab before a meal and it shoots up I then have to give a whopping dose to get it back down but if the timing is just right and I don't go above say 9 everything works fine .