WHAT GIVES?!
When it comes to dosing, pizza can be one of the most difficult foods for the diabetic community to master. Unlike foods with high protein/lower carb ratios, or even those with quick in/out carbs (i.e. fruits), pizza's high fat and carb combo can spell frustration for managing glucose levels.
THE AFTERMATH
After eating pizza, you may see a rather modest rise in blood glucose levels from initial digestion of certain elements of the pizza. This slight increase is typically followed by a lull in any meaningful change in glucose levels. As this lull can last anywhere from 30 minutes to a couple of hours, one may think that they've outsmarted the carb monster. After the body moves on from digesting the simple carbs from the pizza crust, the fat from the cheese and toppings begins to wreak havoc. This secondary push usually comes with a notable amount of insulin resistance, requiring more insulin to be thrown at the carbs than one typically would. A very stubborn high that lasts for several hours can quick accompany this secondary push.
SPLIT AND EXTENDED BOLUS STRATEGIES
In order to prevent a spike in blood glucose levels, while also preventing a low, a split bolus (multiple manual injections) or an extended bolus (CGM "drip") can be used. These strategies call for a modest insulin dosing upfront, with an additional dosing(s) over the course of the next several hours. This delayed approach helps provided a longer insulin coverage period than an all-at-once dose would, as most of those units would be already metabolized by the time the secondary push hits.
WILD CARDS
To add further insult to injury, variations in pizza such a 1) crust thickness, 2) amount of sauce, 3) amount of cheese, 4) additional toppings, etc. can all affect the strategy used for dosing. Generally speaking, though, a multiple or extended bolus is most always required for best coverage.
As with most things diabetes, it's important to keep in mind that there's not a one-size-fits-all approach. Given pizza's unrivaled popularity and seemingly never-ending variations, one must be patient and prepared to fine-tune an approach that works for them over the course of several meals.