One of the trickier things with Fiasp is high-fat meals where delayed digestion is a factor. I’ve seen a number of people suggest that you do a delayed bolus for that, but I’ve been confused about exactly how or whether to combine that with pre-bolusing. Even with the fat, I’ll get some effect from the carbs early on, and if I don’t get my BG down ahead of time it’s really hard for a later dose to catch up. I basically see two peaks, an initial bounce that if I do things right usually levels off at 130-150, then another later one that will go up over 200 if I don’t get ahead of it. So once I see that initial one top out, I take another bolus for the anticipated second one. I suppose I could just program a dual wave, but that seems to diffuse the effect too widely.
What @Scott_Eric says about this matches what I’m experiencing. One of my hardest challenges is that my biggest carb intake tends to be at the midday meal, but I bike commute and I really need to have minimal IOB by the time I’m riding home or I’ll go super low. I’ve been experimenting with setting a temp basal of essentially zero a couple hours ahead of departure, but with Novolog it never seems to work. I basically have to just tolerate a big post-prandial spike so I still have a high enough BG to get home on without plummeting into the 60s or worse. “Don’t correct too much or you’re going to crash on your bike ride!”—which is kind of absurd. Since switching to Fiasp the temp-basal thing is working MUCH more effectively–whatever the graph shows, the effect is that it clears more rapidly.
OT, but it was exactly this quandary that I was hoping 670G auto-mode would iron out for me. I hate having to do all this head-scratching, tea leaf-reading to predict what I have to do now to account for what’s going to happen 3 hours from now and then what if it rains and I can’t ride, or if I think it’s going to rain and then it doesn’t so I could ride except I have IOB and blah blah blah. Gimme a smart pump that can figure all this out for me! I thought. Unfortunately the darn thing did a worse job than I could do manually, while locking me out of the controls that would let me adjust things on my own except by dropping out of auto entirely. Which kinda defeats the whole purpose. /digression