Dear Pastor Jeff,
So then isn't 1.6 your 'new normal'? Of course there is a difference between kidney donors and non-donors. We only have one kidney, so creatinine is higher than pre-donation. But we also do not have kidney disease, so the higher level tends to be stable. The CKD3 thing would only work if you were not a donor and had declining kidney function.
I'm not sure about your nephrologist telling you scary stories. Who can make a prediction like that about 30 years down the road?
I do think donors (and everyone!) should maintain a good weight and blood pressure, get plenty of exercise and stay away from NSAID's. These things will not hurt your future 90 year old self's kidney function!