SHAFAQNA – The Grand Ayatollah Seyyed Sadeq Rouhani answered a question about fasting for diabetics.
Question: Is it Wajib for diabetics who suffer from acute thirst to fast?
The Grand Ayatollah Rouhani: Technically these individuals are known to be suffering from acute thirst; if fasting for these individuals is difficult or not possible, it is allowed to do Iftar and instead pay (religiously specified) amount of food to a poor. And if after Ramadhan is well enough to fast, it is Wajib to do Qadha fasting; otherwise it is not Wajib to do Qadha.
Source: PERSIAN SHAFAQNA