Provera is typically prescribed during the second half of the month long cycle or, during the luteal phase. That is why the prescription typically describes taking the medicine days 16 through 25. Upon receiving the medicine at first, you will likely not know where you are in your cycle so you start the medicine immediately. Within 1-3 days of finishing your 10 day course, you should have a menstrual cycle. This cycle can be significantly heavier than your usual cycle. The day you start bleeding after the medicine, is CYCLE DAY #1. From that day forward, count to day 16 and that is when you initiate your next 10 day course and so on... Patients are typically put on at least a 3 month course. Each subsequent cycle should become more manageable.
A couple words of caution: