FIL's creatinine level recently rose to 5.2. Is there anything we can do to help?

FIL's creatinine level recently rose to 5.2. FIL does not do dialysis, but gets the weekly shots to help with his anemia (which is a condition of CKD). We are told once the creatinine level reaches 5.5, hospice service will be required. Can we use diet to help lower his creatinine level? We have no idea what to expect. I've read that creatinine levels can come down, bit of a yoyo effect. People can go into hospice and come out. Anything we can do to help? Thank you for your thoughts, experience with something similar and personal stories.