How long after starting the pill for the first time does it take for it to become 99% effective in your body?
It depends on whether you’re taking combination pills or progestin-only pills.
You can start the combination pill at any time. If you start within 5 days after the start of your period, you’re protected from pregnancy right away. You won’t need to use a backup method of birth control (like a condom). That means that if your period starts on a Wednesday morning, you can start the pill up to the following Monday morning to be protected right away. If you start at any other time during your menstrual cycle, you’ll be protected from pregnancy after 7 days of using the pill. Use another method of birth control — like a condom — if you have vaginal sex during that time.
You can start the progestin-only pill at any time. Use another method of birth control — like a condom — if you have vaginal sex during the first 48 hours of progestin-pill use — protection will begin after 2 days.