There are figures for required minimums and that sort of thing, but my experience is that everyone is different and processes food in their own way and with their own level of efficiency. EGFR is an estimate of your kidneys efficiency. not an absolute, although it may be the best we have. Nine years of dealing with my ESRD has lead me to say that it's a trial and error process. Make changes in your diet, see what your labs say and then make revisions based on your labs.