New research revealed that some emergency contraceptives might not be effective for women at higher body weights.1

“There is limited research about the relationship between the efficacy of emergency contraceptive [EC] pills and body weight,” says Kelly Cleland, MPA, MPH, researcher at Princeton University and director of the American Society for Emergency Contraception in Princeton, NJ. “The evidence we do have suggests that levonorgestrel EC may have reduced effectiveness in individuals who weigh 165 pounds or more, and possibly no effectiveness for those who weigh 176 pounds or more.”

The clinical trials of ECs have limitations. For instance, there were some pregnancies, and there were fewer numbers of emergency contraception users in the higher weight categories. Also, their weight was self-reported, Cleland says.

“[Prior] studies were not designed to answer the question of weight and efficacy,” she says. “But because this is a clinically important question that potentially impacts millions of people, we take this information seriously.”

In 2013, European regulatory authorities approved a label change for Norlevo, an EC product, to warn that it was less effective in women weighing 165 pounds or more and ineffective in women weighing more than 176 pounds.1

“But European authorities reversed the labeling decision in July 2014, less than a year after this change was made,” Cleland says. “And the U.S. Food and Drug Administration determined that the existing data were not compelling enough to warrant a label change.”

Reproductive healthcare providers might let women know about potential drawbacks in using EC because many women may not know that their body weight could reduce the drug’s effectiveness. “From what I can see, the potential lower efficacy of levonorgestrel for users with heavier body weight is not at all well-known,” Cleland says. “Pharmacies, generally, do not have signage about this issue. Because it’s not on the label for levonorgestrel EC products, consumers would have to find this information somewhere else.”

Levonorgestrel is the easiest EC for women to obtain. Other ECs might be poorly stocked and carry additional barriers to access. “We certainly believe that all remaining barriers should be removed,” Cleland says. “At the same time, I think it’s really important that people understand the limitations of the product so they can make an informed decision when they need emergency contraception.”

Ulipristal acetate is a good solution, Cleland says, “although it, too, appears to have a limit to efficacy. Some research shows that it may be ineffective for users who weigh more than 195 pounds.”

The main drawback to ulipristal acetate is its limited access. “It is still a prescription-only product,” Cleland says. “Even though it has been approved for the U.S. market for nearly 10 years, awareness among providers and patients remains low.”

Recent studies show that pharmacies do not routinely stock ulipristal acetate, so it can be difficult to obtain, she adds.

“Ulipristal acetate is an extremely safe medication, especially in the dosing used for EC. There’s no reason that it should continue to be a prescription-only product,” Cleland says. “In fact, ulipristal acetate is over the counter in Europe, and we hope it will be over the counter in the U.S. very soon.”

Another possible option — after more research — is for women with higher body mass index (BMI) to take a double dose of levonorgestrel.

There is some evidence that doubling the dose of levonorgestrel EC in patients with BMI greater than 30 kg/m2 might result in similar blood levels of levonorgestrel as women with BMI less than 25 kg/m2 who take the regular dose of 1.5 mg, Cleland says.

“But this is still preliminary pharmacokinetic research,” she adds.

An alternative option, and the most effective option for everyone, is the copper intrauterine device (IUD), Cleland notes.

“It is nearly 100% effective, and its efficacy is not impacted by body weight,” she says. “We think it’s important to make sure providers and patients know this is an option.”

IUDs are not for everyone, and no patient should be pressured into using one, she adds.

“For people who weigh more than 165 pounds, we really encourage them to call a healthcare provider or family planning clinic to get a prescription for ulipristal acetate,” Cleland says. “There also are online pharmacies that ship ulipristal acetate EC after a consultation with a physician.”


  1. Cleland K, Wagner B, Smith NK, et al. My BMI is too high for Plan B: A changing population of women seeking ulipristal acetate emergency contraception online. Women & Health 2020;60:241-248.