Re: kidneys

If you have impaired kidney function, then the fast will burden these organs much more, bearing in mind I have already mentioned that malfunctioning kidneys are construed as a contraindication to fasting.
While eating, your kidneys perform under less stressful and burdensome conditions, but while fasting, there is a huge burden placed upon your kidneys in elimination, just as there is on the Liver and the other organs of elimination.
My advice would be to have that kidney function test PRIOR to the commencement of a fast to establish the safety or otherwise of whether a fast is advisable or not.

Chrisb1.