Potassium level was 6.6, in hospital and went down to 5.0, now elevated a little again, do kidneys recover from this & any foods good that can help?

Other way around: Potassium (K+) levels vary from hour to hour based on intake via food and supplements. Its the kidneys job to eliminate excess and prevent loss when K+ is low. K+ range outside of approx 2 to 8 is not compatable with life and the 1st effect will be to stop your heart. A dammaged kidney may not effectively regulate K+ but isn't injured by K+. To reduce K+ reduce foods high in potassium.