I really struggle sometimes with post-prandial readings, even though I low-carb (under 50g carbs per day, usually nearer 30g). My main problem is that quite often the spike comes three, four hours (or more) after I've eaten. I'm trying injecting earlier before meals, and with a correction dose a couple of hours after I've eaten, but I'm wary about stacking insulin, going hypo and having to eat extra. (I'm trying to lose weight to improve my insulin sensitivity.) There doesn't seem to be a pattern with what causes a delayed spike, either.