How long does it take to show a difference in bloodsugars when changing active insulin time with the 780?
The same time it always takes insulin to change your blood sugar, which is highly variable. Changing that setting doesn’t affect how any single bolus works in the least. It only affects the IOB countdown timer, trying to make the clock match your own reality.
My experience was with the 670, but I think the AIT adjustment was basically the same. Its relationship to actual insulin duration was purely notional. Rather, its main function was in adjusting the Automode algorithm to be more or less aggressive over all. It was (is?) pretty much the ONLY parameter you could use to do that The logic, as I understood it, was that the algorithm is calculating the delivery of a “micro-bolus” every five minutes, and it’s using AIT to avoid “stacking” those doses and sending you hypo. So if you found you were chronically running low, increasing AIT would ameliorate that. Or if—as I think the broad majority of people found—the algorithm was letting you run higher than you wanted, you’d drop it down. I had mine lowered to 2 hrs, the hard-wired minimum, and it still wasn’t enough. But this was legendarily the single most powerful adjustment you could make. Other standard parameters like I:C and Correction ratios were actually blocked out of Automode. You put them in, but they were only operational in Manual.
To answer your question, in my experience the change to AIT showed noticeable effect on my overall BG within 24 hrs. Wasn’t enough, mind you, but it definitely moved it in the right direction. If I could have dropped it to 1:45 I might have stuck with that system.
Again, this pertains to the older version of the pump/algorithm, but I think it still applies. Perhaps someone with more recent experience will weigh in.