Q: Why does my period always come at the end of the white pills and not the beginning?
A: There are typically 28 days in a menstrual cycle and only 21 active hormone pills in a birth control pack. Menstrual cycles tend to be shorter when you’re taking birth control pills and your cycle is controlled by the active hormones in the 21 colored pills.
As long as you’re taking your birth control pills every day, your cycle should keep to a regular 28 days, and your period will start on the last couple white pills each month and may last a couple days into the next pack of active pills. Most women start their period about 25 days after the first active pill in a pack. With 21 active pills that means your period will start around the 4th white or inactive pill.
It is important to remember that your menstrual cycle will take some time to adjust to the patterned hormone increases caused by birth control pills. On average it can take at least one to two months of continued use to regulate your menstrual cycle. Breakthrough bleeding, missed periods and lighter than normal periods are common when taking birth control.