Why do I get a delayed blood sugar spike after pizza?

Hi Emily, the frustration you are feeling is incredibly common in the diabetes community—in fact, this specific meal is so notoriously difficult to manage that people often just refer to it as the "pizza effect."

When you eat a meal that is exceptionally high in both dense carbohydrates (the thick crust) and heavy dietary fats (the melted cheese, meats, and oils), your digestion process changes significantly. High amounts of fat physically slow down how quickly your stomach empties its contents. So, instead of the carbohydrates digesting and hitting your bloodstream in the usual one-to-two-hour window, their absorption is drastically delayed.\

Because of this slow digestion, the rapid-acting insulin you took right before eating often peaks and finishes working completely before all the carbohydrates have actually entered your system. This timing mismatch can cause you to drop low shortly after eating, only to experience a massive, stubborn delayed blood sugar spike after pizza several hours later—usually right when you are falling asleep.

To tackle this, many insulin pump users utilize an "extended" or "square wave" bolus feature, which delivers a portion of the insulin upfront and slowly stretches the rest out over a few hours to perfectly match the slow-digesting food. If you use multiple daily injections (MDI), some people find success by splitting their dose: taking part of it before the first slice and the rest an hour or two later. Since everyone digests fat at a slightly different rate, it takes a bit of trial and error to find the exact timing that works for you.