If it exceeds 15 days and this is the case, this is Istihadah and she has to perform Ghusul and pray.

What is the minimum period of days of purity? For example after every 15 days I get my menses, is this considered as menstruation, or is another blood? Considering that I went to the doctor and closed the fallopian tubes

Menstruation and post-natal bleeding | March 7, 2014 4:59 am
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My menstrual period is irregular due to poly cystic ovarian syndrome,that means sometimes I have menstruation and sometimes I don’t, so I have to take special pills to create the bleeding.
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I have a question. a friend of me is pragnant a few days ago, she was bleeding and now she is not pragnant anymore and still bleeding. Does she have to pray?