How Long After You Start Taking Birth Control Is It Effective ?


Birth control pills are a practical, effective and easy-to-use contraceptive choice. Used correctly, the pill is more than 99 percent effective; however, user error, including missed pills or starting a pill pack late, is responsible for most birth control failures. Know how to take your pills when you start oral contraceptives and when you can rely upon them as your primary form of birth control.


Typically, you will start your birth control pack the Sunday after your period starts, but you can opt to begin your pill pack on the first day of your period. This provides ample time for the pill to work, effectively preventing pregnancy. The pill works in three ways. First, it prevents ovulation. Should ovulation occur, the pill also thickens cervical mucus, providing a barrier, and thins the uterine lining, making it less likely for implantation to occur.


Several types of birth control pills are on the market today. The most common pill is a combination birth control pill that relies on both estrogen and progesterone to prevent pregnancy. This pill may use one dose of hormones throughout the cycle or may change the hormone levels through the menstrual cycle. The progesterone-only mini-pill is somewhat less reliable but works well for women who cannot tolerate estrogen. The guidelines regarding effectiveness are different for these two types of pills.

Time Frame

If you begin a new pack of combination birth control pills within six days of the start of your period or six days from an abortion, your birth control pills will be effective immediately, according to Birth-Control-Comparison. If you start a pill pack at another time, you should use a backup method of contraception until you start your next pill pack or simply wait to start the pill until your next period begins. Some women may be more comfortable using a backup method for the first seven days after starting the pill.

The Mini-Pill

If you are taking the progesterone only mini-pill rather than a combination birth control pill, you should take the pill for one full 28-day cycle before relying upon it as your sole method of contraception. The mini-pill is less effective than estrogen and progesterone-based pills, and cycles are commonly irregular when taking it. It is especially important to take the mini-pill at the same time each day to prevent pregnancy.


The guidelines regarding pill effectiveness allow the hormones in the pill time to work in your body to prevent ovulation. Waiting until your period begins to start taking the pill ensures that you are not already pregnant and that you have not already ovulated. Talk with your pharmacist or doctor if you have additional concerns or questions about when your birth control pills will effectively prevent pregnancy.

Watch the video below to learn more about Birth Control Pills:



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