Eating same thing taking same amount of insulin , getting different blood sugar readings , that’s the anomaly of diabetes , these days I don’t question it , it just happens , it just proves that it not just about taking insulin and eating, many other things affect blood sugar readings , as long as my readings stay between 5 and 9 I’m happy if they are outside that ( which these days is rare ) I don’t panic.I just deal with it , no matter how hard we try we are never going to get perfect blood sugars all the time