What is the ruling on fasting Ramadan for someone who lives in Canada, where fasting hours reach 18 hours, and has suffered from kidney stones and been advised to drink plenty of water to reduce salt deposits?

The fear of contracting an illness is akin to the fear of its aggravation, in terms of permitting breaking the fast. However, the need to drink water to prevent kidney stones is considered as follows: If drinking at night is sufficient to dispel the fear, then breaking the fast is not permissible. But if drinking during the day is necessary and there is a fear of illness, confirmed by a trustworthy doctor, then breaking the fast is permissible. If the fear is alleviated by breaking the fast on some days, then you should break the fast for the period that removes the fear, and fast the remaining days.