I feel like this 2 hour/4 hour thing is old Diabetes theory still lingering. It’s only in VERY recent years that the common Endo is believing you can stay in range post carbs. Joslin and other diabetes innovators aside. It’s also only in recent years that we’re starting to evolve away from the carb-heavy food pyramid guidelines. Heck, we still see posts often here about “my endo/nutritionist/DE/fill-in-the-blank” says I need to eat more carb".
The common doctor catering to diabetics is so scared of lows, that they EXPECT us to be high and out of range in the post-prandial. Within two hours, though, the bolus should have you back in range. Not necessarily at your target BG, just in range. “Excellent management” used to be defined as obtaining 140 mg/dl (7.8 mmol) within 2 hours of a meal.
I have the 5th edition of Pumping Insulin (2012, I think 6th is the most recent), and I feel like it is already largely outdated. This is an image from the chapter about corrections:
You can see that the Goldilocks “just right” correction factor brings you down over the course of 5 hours, but should be leveling off around the 3-4 hour range.
In that example, the “too low” value still took them 3 hours to get back down to 100, but it’s too fast, because they’re going to continue dropping beyond that. 3 hours feels like a lifetime of elevated BG to me! But that was before we had options to suspend basal.
Now, we’re seeing a lot more options to tightly control the numbers. Low carb/moderate to high protein and fat diets, high carb/low fat diets, greater availability of CGMs, looping, commercial pump semi-closed loops, super-bolusing, etc…
We’re in a great transition where 100% TIR is actually becoming achievable WITHOUT increased risk of severe hypoglycemia, but all the terminology and medical professional mindset hasn’t caught up yet. I think it’s why there’s so much confusion now. We’re really striving for perfection. We want the BG right back at target as soon as possible, and we forget that it was never even expected just a few years ago.