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How weight impacts the morning-after pill

by Dr. Margo Harrison
Julie Medical Advisor
Morning After Pill

Does the Morning After Pill have a Weight Limit?

Technically no, but it’s complicated. A few studies have shown that the effectiveness of the morning-after pill does decrease in people who weigh more than 165 pounds or have a body mass index (BMI) over 25. Why? Unfortunately, we don’t really know.

There is only preliminary research testing the efficacy of the morning-after pill on people with a BMI over 25 and 30. The research that led to the morning-after pill’s creation in the 1990s didn’t take into account different body weights, which is one of the reasons that we know so little about its effectiveness today.

The few studies that have been done aren’t definitive, and some even contradict each other. More research needs to be done, especially considering the average weight of women in the US is 170 pounds. We need emergency contraceptive research to catch up and be inclusive of everyone. In the meantime, let’s go over what we do know.

In 2009, a study found that women taking emergency contraception with a higher BMI had a 3x greater risk of pregnancy than women with lower BMIs. Doctors hypothesize that in overweight people, drugs might take longer to absorb into the bloodstream or end up stored in fat in the body instead of circulating.

Does BMI Impact Effectiveness?

Because the research is limited, even experts don’t know the weight at which the morning-after pill’s efficacy begins to decrease. But here’s where the science is at right now:

BMI 25+

The emergency contraceptive pill is safe to use for women with BMI of 25 or higher. In terms of how effective it is at preventing pregnancy, the research is not conclusive. There is clearly reduced efficacy, but if 100 women were to take Julie, about 95 of them would not get pregnant if the medication is used as directed.

BMI 30+

It is also safe for women with a BMI over 30 to take emergency contraception. Here again, efficacy is reduced, but of those 100 women discussed before, still over 90 of them would not get pregnant if they use the medication properly and have not already ovulated.

Side note: BMI is a total measure of your body fat based on height and weight. Not sure what your BMI is? Use this helpful calculator from the NIH.

Even though we have seen effectiveness decrease with higher BMIs, these studies have shown that the morning-after pill (aka levonorgestrel) is still safe and effective at reducing the risk of pregnancy. For example, one study showed that the risk of pregnancy for women with a BMI over 30 who took levonorgestrel was 2%, compared to 1.2% for the entire group, which included people with lower and higher BMIs. So while effectiveness decreases as BMI increases, the morning-after pill can still be effective no matter your BMI.

In fact, the FDA has approved oral levonorgestrel, aka Julie, for everyone, regardless of weight. So if you’re questioning taking Julie because of your BMI, know that taking it can’t harm you, and there’s a chance that it will work. However, there are alternative emergency contraception options that are proven to be more effective in people with BMIs over 30.

Alternatives to the Morning-After Pill

While Julie and other OTC morning-after pills are safe to use, there are more effective alternatives for people with a BMI over 25, like Ella and the copper IUD.

Ella: For women who weigh 165-195 pounds, doctors recommend Ella, an emergency-contraceptive pill containing ulipristal acetate. However, the efficacy of Ella also decreases with increasing BMI. Ella can be taken up to five days after unprotected sex and requires a prescription from a doctor or nurse.

Copper IUD: Wrapped with a copper coil, the copper IUD contains no hormones and can be inserted by a healthcare professional up to five days after unprotected sex. Weight does not impact its efficacy, making this a great option for people with higher BMIs. The copper IUD has a failure rate of .1%, meaning that only 1 in 1,000 women who get it inserted within 5 days of unprotected sex will become pregnant. The only downside is that you need to get an appointment with a healthcare professional immediately to get one inserted in time.

Does Double-Dosing Work for People with a High BMI?

Some studies have shown that the concentration of levonorgestrel in people with a BMI over 30 was half that of the concentration in people with a BMI under 25, so doctors considered doubling the dose. One study showed that the double dose (3mg) brought the level of levonorgestrel up in people with a BMI over 30 to 1.5mg, the same level of women with a BMI under 25. But, a follow-up study showed that the double dose had no clinical improvement in pregnancy prevention.

Taking the Morning-After Pill Can’t Hurt

There’s no doubt that research about the morning-after pill efficacy in people who weigh more than 165 pounds is confusing. However, a review of four World Health Organization studies concluded that pregnancy rates for individuals with various BMIs who took the morning-after pill stayed below 3%, which is reassuring. So though we cannot be super definitive about the efficacy of the morning-after pill for women with higher BMIs, we do know that overall, the medication still reduces the chance of getting pregnant by a lot.

If your BMI is over 30 and you’re wondering whether the morning-after pill, like Julie, will work for you, we unfortunately don’t have the answer. If possible, and if it’s something you want to do, getting the copper IUD inserted is the most effective way to protect yourself against pregnancy after unprotected sex. If that isn’t an option, taking Julie or Ella is the next best thing. Even if it doesn’t work for you, there is no harm in taking it. It cannot harm you or a fertilized egg, if you do end up being pregnant, won’t affect your fertility, and doesn’t cause any serious side effects.

Although the information above may be useful, it shouldn’t replace the advice of your healthcare professional. For questions about birth control and other women’s health issues, please talk to your healthcare professional.