Salaam, my husband goes for dialysis three times a week, he is also fasting but many people tell him his fast is not valid. Can you please let us know that is it permissible for him to fast during ramadan?
He has dialysis in the morning for 4 hours and three to four types of chemicals are added to his blood for cleaning which are removed afterwards.

In the name of Allah, Most Compassionate, Most Merciful.

Answer

Fast will become invalid if anything is inserted through a normal open orifice such as the mouth, nose or private parts and reaches the stomach or the brain. (See Hidayah, vol 1, P220)
When dialysis is performed the above conditions are not met, i.e. the substances do not reach the stomach or brain and also the substances do not enter through a normal orifice, therefore the fast would remain as valid.

Only Allah knows best.

Written by:

Sayeedur Rahman

Darul Ifta, Birmingham