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. Some doctors have hypothesized 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. Other studies contradict this hypothesis, as doubling the amount of the medication in the body does not impact its efficacy.

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.

We totally acknowledge that research here is lacking, especially considering the average weight of women in the US is 170 pounds. At Julie, we will always aim to deliver transparent and factual education while striving for inclusivity of all body types. So as we learn more, we will share with you. In the meantime, let’s go over what we do know.

Does BMI impact efficacy?

We’ll start with the basics. Pregnancy risk after unprotected sex is over 10%. That means for any act of unprotected penis-in-vagina sex, 10 out of 100 women will become pregnant. That’s because timing is everything – where you are in your menstrual cycle plays a huge role in your risk for becoming pregnant, and not everyone is ovulating at the same time. So baseline risk = 10%.

Now let’s compare how the morning-after pill reduces pregnancy risk for different BMIs:

• BMI less than 25. For those with a BMI under 25, the morning-after pill reduces pregnancy risk to 1.7% when the medication is used as directed.
• BMI 25+. As BMI increases, the morning-after pill is still very safe to use. And while there is clearly reduced efficacy with increasing BMI, the morning-after pill still reduces the risk of pregnancy. For women with a BMI between 25 and 30, pregnancy risk is 2.5% when the medication is used as directed.
• BMI 30+. It is also safe for women with a BMI over 30 to use emergency contraception. Here again, efficacy is reduced, but pregnancy risk is 5.8% (still better than a 10% risk) when they use the medication properly and have not already ovulated.

Alternatives to the morning-after pill

While the Julie Morning After Pill™ and other OTC pills are safe to use, there are more effective alternatives for people with a BMI over 25, like Ella® and the IUD. The only catch is that these have an extra step – you’ll need to involve a medical provider.

• Ella®: Ella®, an emergency-contraceptive pill containing ulipristal acetate, is a more effective option for women weighing between 165 to 195 pounds. However, the efficacy of Ella® also decreases with a BMI over 30. Ella® can be taken up to five days after unprotected sex and requires a prescription from a healthcare provider.
• An IUD: IUDs (both copper and hormonal) can be inserted by a trained 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 (it’s actually the most effective for those with lower BMIs, too). The copper IUD has a failure rate of 0.1% and the hormonal IUD has a failure rate of 0.3%, making both forms a very effective form of emergency contraception. The biggest obstacle to using an IUD as emergency contraception is that it needs to be inserted by a trained healthcare professional within five days after unprotected sex for it to be effective as emergency contraception.

Does double-dosing work for higher BMIs?

In short, no. There is no evidence that doubling the dose will further reduce pregnancy risk for those with a BMI over 30.

At one point researchers thought they were onto something because early studies showed that the blood concentration of levonorgestrel in people with a BMI over 30 was half that of the concentration in people with a BMI under 25. So why not double the dose? One group found that the double dose (3mg) did, in fact, increase the blood concentration of levonorgestrel in people with a BMI over 30 to the same level of women with a BMI under 25. However, a follow-up study showed that even with similar blood concentration levels, the double dose resulted in no clinical improvement in pregnancy prevention for individuals with a BMI over 30. In other words, there’s more to it than just concentration in the blood.

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 of all BMIs who took the morning-after pill as directed stayed below 3%, which is reassuring. Although 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.

While we love to share useful and helpful information, the above shouldn’t replace the advice of your healthcare professional. For questions about birth control and other women’s health issues, please talk to your doctor.