Q12: What about a person who suffers from kidney failure and has to undergo dialysis twice a week and each dialysis takes four hours; what should he do with regard to fasting if he is unable to fast?

A12: If he finds it necessary to break his fast, he may do so and then make up the un-fasted days afterwards. But if dialysis itself entails entrance of something into his gut from outside, then by itself it invalidates the fast. And Allah knows best.