Plan B does not have an official weight limit, meaning there is no strict cutoff that prevents people above a certain weight from using it. However, research suggests that Plan B may be less effective in individuals who weigh more than 155 pounds (70.3 kilograms) or have a body mass index (BMI) of 30 or higher

. Key points about Plan B and weight:

• Plan B contains levonorgestrel, and studies indicate that its effectiveness in preventing pregnancy may decrease as body weight or BMI increases, particularly above 155 pounds or a BMI of 30

• Despite this, Plan B is still safe to use regardless of weight and can substantially reduce the chance of pregnancy if taken within 72 hours after unprotected sex

• Planned Parenthood and some experts recommend that people over 155 pounds consider alternative emergency contraception methods, such as the copper intrauterine device (IUD) or Ella (ulipristal acetate), which may be more effective for higher body weights

• The exact reason for decreased effectiveness is not fully understood but may relate to how levonorgestrel is metabolized and its concentration in the bloodstream

• There is no FDA-mandated weight limit on Plan B, and it remains a recommended option for emergency contraception for all weights, with the caveat that other methods might be preferred for those with higher weight or BMI

In summary, while there is no formal weight limit for Plan B, its effectiveness may be reduced in people weighing over 155 pounds. Those individuals are advised to consider other emergency contraception options for better efficacy, though Plan B can still be used safely