(An excellent reason to avoid hydrogenated fats as well; they accumulate in your capillaries and block blood flow!)
My mother died of kidney failure associated with diabetes. The doctors looking at her blood work failed to take into account the loss of body mass due to amputation of her legs above the knees and miscalculated the actual high % of creatine (IIRC) in her blood. While at some point they might have taken some action, maybe dialysis, It probably would not have made much difference long term. She was in her late 70s, overweight, and if she wanted cookies she had cookies. ("Don't bother her, let her have what she wants! Its her only pleasure!") Said her Daughter my sister who on her way to the same end.
Remember Future Diabetics! Remind your doctors to adjust total body mass when doing blood work calculations after you get those limbs amputated! (slightly bitter sarcasm / )
They were measuring creatinine. They probably were using the “estimated Glomerular Filtration Rate”, eGFR, rather than the more precise “measured GFR”.
But if a diabetic won’t change their diet it won’t matter which test they use. The insidious thing about diabetes is that they don’t feel the damage until it’s far too late. If it caused them pain early on maybe they would take it seriously when they still had a chance.