Hi, all! At midnight I awoke with chest pain that lasted for about 4 hours. I had eaten some forbidden foods yesterday (off the kidney diet list) and went to the heart doc this morning. I told him about my reaction to foods not on kidney diet list and about my GFR. He said that food can't cause such a sudden buildup in potassium or phosphorus - that my kidneys would filter all that out. It's amazing to me how many doctors think that GFR at stage III is nothing to worry about!! Though my GFR went back up from 53 to 72 a month ago, not sure what it might be now. Question: Has anyone here with reduced GFR at stage II, III, or IV ever had chest pain/heart issues due to the build-up of potassium, phosphorus, calcium, or magnesium from food they ate? I can feel the difference pretty soon after straying from the kidney diet - either that night or the next day. Does anyone else here also feel the difference soon?