Not Fasting During Female Menstrual Cycle
Adding onto what Dr. Irfan Shahzad Sahab summarized, the menstruation cycle deprives women of basic purity which is needed for any Ibadah, therefore, they must make up for their left over fasts once their cycle is over. However, if some medication can be used to postpone menstruation, then it can be used but subject to doctor’s advice. Please also see for more details : Discussion 47366
JazakAllah for sharing the detailed thread.