I take birth control every day. i normally start my period on friday or saturday but i haven't started yet. is this concerning?

Variation: Even though you are on a pill that regulates your periods, it is still normal to have some variation in your periods, not starting a period for a few days after the last hormone containing pill of your pack is common. Your body still has some fluctuating hormones of its own that can cause missed or delayed periods, break through bleeding and variations in flow from month to month.