Calm Logic said:
With a CGM, what number is un-ideal anyway, after eating carbs? In addition to length of spike.
That is a matter of great dispute and it's not clear to me that anybody knows the answer to that, although many end up obsessing over that in ways that are probably un-important and counter-productive.
The more important thing to look for is probably how quickly your body clears those spikes and how those spikes compared to those of other people. For example, if I eat a bowl of plain white rice as my first meal in the morning, I'd expect to see a gigantic spike, perhaps as high as 200 mg/dL, but I'd also expect that to return to baseline within 90 minutes to 2 hours VS stalling out at a higher level. Now if I lost 50 pounds, I suspect that spike would be shorter, but that isn't to say such a tall spike in itself is dangerous, as long as it's limited to a brief period of time. There are people who will dispute this and suggest that any spike above 140 mg/dL is non-ideal, but I struggle to support their rationale.
If, on the other hand, I spike to a high level and stay there for hours where the return to baseline is a much slower process, that would suggest significant insulin resistance/diabetes. Under those conditions, not just my RBC, but also my internal organs would be subject to higher degrees of glycation, as the spikes would reach them as well and remain more sustained. Everyone is going to agree that's a bad thing and I don't think any dispute exists there.
If, going further in that direction, my blood sugar is regularly staying closer to 200 mg/dL or higher and meals knock it in various directions at various times, that would be indicative of uncontrolled diabetes and be the worst possible scenario.
Then there will be some true processed food enthusiasts/addicts who will top even that, regularly maintaining double-digit A1cs, while helping their treatment teams afford to make payments on their luxury cars and private planes.
I split up the worse outcomes into more categories that necessary to help you contextualize that even if you're not in the very best category, it can always be worse.