1 Question: I become extremely thirsty while fasting. Can that be an excuse for breaking my fast?
Answer: If a person who is observing fast becomes thirsty and it is feared on his part that fasting might be harmful to him or it is extremely difficult for him that it is not bearable normally, it is permissible for him to drink at the time of extreme thirst to the extent of necessity only in which case his fast becomes void and he should not eat or drink more than that out of respect for the month of Ramadhan and should continue to restrain himself for the rest of the day, as an obligatory precaution. He should observe the qadha of that day after the month of Ramadhan. If he is not fasting in the month Ramadhan and he has enough time to perform the Qadha of his missed fast, he can break his fast.sistani.org/25354