wr115,
you are best to have a kidney function test before a water-only-fast, just to make sure...
Shelton had this to say re' the kidneys as a possible contraindication to the fast............
"In cases of inactive kidneys accompanied by obesity. In such cases it is said that the tissues may be broken down faster than the kidneys are able to eliminate them. This I doubt. I know of no reason why the tissues of the body should be used up faster at this time than at other times. It is true that there is increased elimination during the fast but this is not so great as to constitute a great burden upon the kidneys. I have repeatedly fasted cases of Bright's "disease" and cases of kidney stone, kidney abscess and pyelitis with distinct benefit in all such cases".......................... http://www.soilandhealth.org/02/0201hyglibcat/020127shelton.iii/020127.ch25.htm
............and a liver-function test would also be useful.