Mirena may also affect heavy periods in other ways
The number of spotting and bleeding days may initially increase but then typically decrease in the months that follow. Bleeding may also continue to be irregular.
Call your healthcare professional if bleeding remains heavier than usual or you do not have a period for 6 weeks during Mirena use.
After your body adjusts, the number of bleeding and spotting days is likely to decrease, but may remain irregular, and you may even find that your periods stop altogether for as long as Mirena is in place. By the end of year one, about 20% of users have no period at all. Your periods will return once Mirena is removed.