Is it permissible for a patient with an advanced stomach ulcer, who has been forbidden by the doctor from fasting, to break their fast, and is the expiation for that five pounds per day?

It is permissible to break the fast if a trustworthy, expert physician determines it.

If recovery is expected, you must make up the fasts (qada').

If the illness is chronic, you must pay the expiation (fidyah), which is feeding one poor person for each day, with a "mudd" of food (equivalent to 750 grams). Paying the monetary value is not sufficient.