This Is How Plan B Effectiveness Might Vary Based On Your Weight

Plan B is an emergency contraceptive designed to help prevent pregnancy within 72 hours after unprotected sex. However, the effectiveness of Plan B can vary depending on how much you weigh (via Healthline). While Plan B is generally very effective at preventing pregnancy, research suggests that the pill might be less effective in people who weigh more than 155 pounds, or have a body mass index (BMI) of 30 or higher.

According to a 2016 preliminary study published in the journal Contraception, people with a BMI over 30 had lower levels of levonorgestrel in their blood, which is the main active ingredient in Plan B. A 2011 study published in the same journal also found that pregnancy risk was three times higher in participants with a BMI of 30 or higher, compared to those who had a BMI ranging between 18.5 and 25. However, a 2017 research review published in Contraception concluded that the pregnancy rate was low across all weight and BMI categories after taking Plan B. For those concerned about the effectiveness of Plan B for their weight range, there are some alternatives available.

For people who weigh more than 155 pounds, there are a few options available. According to Verywell Health, Ella is another emergency contraceptive that tends to be more effective for those with higher BMIs. That's because Ella contains ulipristal acetate (UPA) instead of levonorgestrel. However, it also requires a prescription and may be less effective for people who weigh over 195 pounds. A copper intrauterine device (IUD), on the other hand, is highly effective regardless of weight or BMI.

Unlike emergency contraceptive pills, a copper IUD needs to be inserted into the uterus during a scheduled in-office procedure. This makes it both long-acting reversible contraception and emergency contraception (via Medical News Today). The procedure, however, can cause some pain and bleeding. Additionally, for some people, the device may later cause their periods to become heavier. Copper IUDs are 99.9% effective and can last up to 12 years.