When is blood considered "istihadah" (non-menstrual bleeding) if it exceeds the usual duration of menstruation, and what is the ruling on blood discharged while taking hormone treatment to stop bleeding?

The default for blood seen by a woman is that it is menstrual blood, unless it is impossible to consider it menstruation, such as when its duration exceeds fifteen days. So, if the duration of the blood does not exceed fifteen days, and the period of purity lasts for thirteen days or more, then all the blood is menstruation. However, if the duration of the blood exceeds fifteen days, or if the blood returns after less than thirteen days and cannot be joined with the first blood, then the woman is in a state of istihadah (non-menstrual bleeding).