Hello, Welcome to Healthcare Magic. I have read your question fully and understand your concerns. Norethisterone is unlikely to stop your periods once it has started. You are seeing your period as your progesterone hormone in your body has decreased. The only way to stop your period is by taking progesterone hormone from outside in the form a pill. But for the progesterone hormone to increase to an appropriate level (to help stop your period) will take around 5 days, by then any way your period would have stopped by itself. So, there is no use in taking norethisterone once your period has started. Of course, it is useful in women who are bleeding heavily and having prolonged bleeding. For them their period would stop in 5-7 days. I guess this is not the case with you. I hope this answer has helped you. Thank you Regards Dr Sunita Sayammagaru