I have PCOS, and the medication I have to take has caused a lot of dysfunctional bleeding. How do I know when my period is?
Wa ‘alaykum assalam wa rahmatullah wa barakatuh.
I pray you are well.
Base Your Period On Your Habit
You need to base your period on your menstrual habit. This is the number of days in your last proper menstrual cycle, the purity between it and the previous proper menstrual cycle, and roughly where it was in the month.
When your menstrual cycle starts, cease praying until it stops. If the bleeding continues for more than 10 days, then the number of days beyond your habit is considered to be dysfunctional bleeding (istihada). So if your habit were 7 days, you would treat everything after day 7 as dysfunctional bleeding if the bleeding continues past 10 days. The prayers missed on the days which turned out to be istihada would have to be made up.
The same would apply to purity. If you have 20 days of purity between the last two proper periods, then use that as the habit if you keep getting dysfunctional bleeding without 15 days of purity between periods. This is when there aren’t 15 days of purity between bleeding, which could be a period.
What If I Can’t Remember My Habit?
Generally, it is religiously necessary to document your habit. Try to figure out how long your last proper cycle was. If this is not possible, do your best to guess the most likely number based on the most likely possibilities.
It would help if you used the above to calculate your periods and treat the rest of the bleeding as istihada.
(Birgivi, Dhukhr al Muta’ahhilin, Kasani, Bada’i al Sana’i’)
May Allah make things easy for you.
Checked and Approved by Shaykh Faraz Rabbani