Plan B Weight Limit and FDA Labeling
The FDA-approved label for Plan B One-Step lists no absolute weight cutoff, but the product's efficacy decreases for individuals with a body mass index above certain thresholds. The manufacturer, Teva Women's Health, updated its labeling to reflect that the drug may be less effective for those weighing 165 pounds or more, and not recommended for those over 176 pounds. For the latest details, see the FDA's Plan B One-Step label information here.
Clinical studies show that levonorgestrel-based emergency contraception, the active ingredient in Plan B, has a higher failure rate in people with higher body weight. A 2011 analysis published in the journal Obstetrics & Gynecology found that the risk of pregnancy increased significantly for those over 165 pounds. This data led to updated guidance from the World Health Organization, which still considers levonorgestrel an option but notes reduced effectiveness at higher weights.
How Weight Affects Plan B Effectiveness
Plan B works primarily by delaying ovulation, and research suggests that higher body fat may alter hormone metabolism and drug distribution. A 2016 WHO statement noted that while levonorgestrel emergency contraception remains an option, its efficacy declines with increasing weight, particularly over 165 pounds. The American College of Obstetricians and Gynecologists also cites this weight-dependent efficacy in its practice bulletins.
For those concerned about weight-related efficacy, alternative emergency contraception options exist. The copper intrauterine device, such as Paragard, is the most effective form of emergency contraception and is not affected by body weight. Ella (ulipristal acetate), a prescription pill, may also be more effective for individuals with higher body weight, though it too has limitations above certain thresholds. A comparison of options is available on the Planned Parenthood website here.
Plan B vs Other Emergency Contraception by Weight
When comparing Plan B to other emergency contraception methods, weight is a key factor in choosing the right option. Ella, which requires a prescription, maintains better efficacy up to 195 pounds compared to Plan B. The copper IUD remains the gold standard for emergency contraception regardless of weight, with a failure rate of less than 1% when inserted within five days of unprotected sex. These distinctions are highlighted by the CDC's medical eligibility criteria for contraceptive use.
Insurance coverage and access also play a role in choosing emergency contraception. Under the Affordable Care Act, most insurance plans cover FDA-approved contraceptives, including Plan B and Ella, without cost-sharing. However, access to the copper IUD may require a clinic visit and can have higher upfront costs. For more information on coverage, see the Kaiser Family Foundation's analysis of contraceptive coverage here.