Craziness, primarily. I had no guidance about changing pump settings, and I couldn’t get a handle on what was needed. I changed IC ratios, DIA (of course), correction factors, and basals, and in the end I just ran out of patience, so the “fault” may not be Fiasp’s.
As well, I didn’t find it significantly faster than Humalog (and that was my primary reason for switching) – 10 minutes at best, but when you’re prebolusing at 30 to 45 minutes, that’s kind of negligible. And while it did smooth out peaks right after eating because it’s so aggressive out of the gate, I’d get a steep rise about four hours after a meal, likely because of its shorter tail.
Sites were also consistently irritated, with a raised red bump still visible as much as three weeks after a pod was removed. I’ve never had this with other insulins, and many Fiasp users don’t experience it.
I’m thinking an increased temp basal, started around mealtime, might tackle that four-hours-later rise, regardless whether Fiasp is pumped or injected. (I don’t have any right now, or I would have tried this already.)