After taking birth control pills, the amount of menstrual flow is on the high side. As birth control pills are hormonal drugs, they can cause the lining to grow in a short period of time, and the amount of menstrual flow when you have your period may be slightly larger than usual. If you have a heavy period on the second day, you can observe and see what happens on the third day. If it decreases slowly, it will not affect your health, as long as it ends within 7 days. If the 3rd day is still on the high side, you can take the right amount of oral medication to stop bleeding, such as Gongxuning capsule or Yunnan Baiyao, you can also go to the hospital intravenous drip into the bleeding medication to stop the bleeding of the purpose, to avoid a large amount of menstrual blood caused by infection and anemia. Therefore, appropriate medication should be regulated to avoid irregular menstruation in the next cycle, there will also be a persistent increase in the amount of menstruation, you can according to their own situation for the corresponding choice of treatment.