How does Plan B (emergency contraception) work?

It seems like everyone is talking about Plan B these days, but to be clear, when people say “Plan B,” they’re usually referring to “post-coital” or “emergency contraception” (EC) in general. EC is used to prevent pregnancy after unprotected sex, and there are actually a few different brands, including Plan B and Ella.

The Caraway Care Team

March 13, 2023

It seems like everyone is talking about Plan B these days, but to be clear, when people say “Plan B,” they’re usually referring to “post-coital” or “emergency contraception” (EC) in general. EC is used to prevent pregnancy after unprotected sex, and there are actually a few different brands, including Plan B and Ella.

While abortion pills end an existing pregnancy, EC prevents pregnancy by stopping ovulation, preventing fertilization of an egg, or preventing implantation of a fertilized egg. However, if a fertilized egg is already implanted, EC won’t work. 

You can take an emergency contraceptive within 5 days of having sex, but the sooner you take it, the more effective it will be. If you can, try to take it within 3 days of having sex to lower your chance of pregnancy by 75-89%. 

While Plan B is easy to get over the counter at most drug stores, it’s not as effective if you weigh more than 165 pounds, in which case Ella is a better option. Talk to the Caraway Care Team to find out what the best EC option is for you, and get an Ella prescription sent to your home or dorm if you need it. 

Reviewed by Sara Levine, MD, MPH, FAAP, Medical Director of Adolescent Medicine

References:
1. Bedsider. (n.d.). Emergency Contraception | Types, Cost, Side Effects & Effectiveness. Bedsider. https://www.bedsider.org/birth-control/emergency_contraception

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