For foods like pizza/mexican/chinese, I actually add a unit or two and extend 10-15% of the bolus out for 3 to 3.5 hours with near perfect flat line levels post-meal. For ALL foods from fast food joints or restaurants (even if it seems “healthy”), I extend 5-10% of my bolus out by at least another 2 hours. That fat hits me hard.
My CDE recommends extending a portion of your bolus out for any meal with 20g or more of fat. 10% of all the fat we eat converts to glucose with about 8 hours of eating it, so a high fat meal is going to have a significant effect on your glucose between 6 and 10 hours later. Roughly 50% of the protein we eat hits us at the 4-6 hour mark, so also be careful about heavy protein meals like steak and burgers.
Like Janice recommended, play with it and see what works for you. Just make sure you’re testing every couple of hours for a meal like that and don’t immediately react to every number you see. An hour or two after a pizza bolus, I may find I’ve dropped into the 70s, but I rest easy knowing that it’s definitely on its way up. As long as it doesn’t continue to drop and I feel okay, I know I’ve spaced things out just fine.