I'm also T1D and yep. That's how it goes. Despite having one of the same two breakfasts pretty much every workday for a decade, it's a crapshoot whether I'll be 300 (very high) when I get to work or 50 (very low) or 110 (good). I just have to adjust when I get in to the office. Most days I deal with it fine, but every once in a while I get fed up with it and want to throw something.