What is the ruling on the prayer of one who takes medication to regulate her menstrual cycle, and menstruation occurs during the seven-day interval between doses, so the period between the two menstruations is less than fifteen days, knowing that this is menstruation from a medical perspective?

The ruling on the duration of menstruation and the ruling on recurring blood are explained in previous fatwas. If blood is seen before thirteen days have passed since the end of the previous menstruation, it is added to what preceded it. If the total of both, along with the period of purity between them, does not exceed fifteen days, then all of it is considered menstruation. If it exceeds that, then the woman is considered to have istihada (non-menstrual vaginal bleeding), because the maximum duration of menstruation is fifteen days, and the minimum period of purity between two menstruations is fifteen days according to the majority of scholars, and thirteen days according to the Hanbalis. Since the recurring blood cannot be considered menstruation, the woman is considered to have istihada, and the ruling on a woman with istihada is detailed in another fatwa.