I was diagnosed with pre-diabetes about 15 years ago. I run about 4.2 when not taking anything. Metformin puts me at 3.5
Potatoes are the only starch that doesn't really do much to me. Waxy ones are better than starch. I always use butter on the potatoes as fat helps slow carb absorption. Same deal for my diabetic parents. It might be a genetic thing.
I've learned over the years which starches are bad for me in order of worst to best. Rice, corn, oats, wheat, barley, potatoes.
Barley is usually the grain go to here since it's fairly safe for me. I use barley for meatloaf and stuffing.
Too much starches cause me rashes. So most meals here are just veggies and some meat. I put butter on all the veggies. We found that using more animal fat lowered our cholesterol profiles by a ton and raised the HDL. I only use olive oil for liquid fat.