What you need to know
- Emergency contraception, including Plan B, does not cause an abortion. It prevents pregnancy before it begins.
- Other emergency contraception options include ulipristal acetate (ella) and certain intrauterine devices (IUDs), which can be used up to five days after unprotected sex.
- Research suggests that Plan B may be less effective for people who weigh 165 pounds or more, so health care providers may recommend ella as an alternative.
A 2023 KFF poll found that nearly three-quarters of people incorrectly believed that emergency contraceptive pills like Plan B can end a pregnancy in its early stages. That misconception continues to circulate online, along with other myths about how emergency contraception works and its side effects.
Between April and July 2026, PGP’s Monitoring Lab analyzed public online conversations related to emergency contraception and found recurring questions and false claims, particularly about Plan B’s side effects, how it works, and whether it’s the same as an abortion pill. (PGP is the nonprofit that publishes Public Good News.)
To separate fact from fiction, PGN spoke with two OB-GYNs about Plan B and other forms of emergency contraception. Read on to learn more.
What is Plan B?
Plan B (also known as the “morning-after pill”) is an emergency contraceptive available without a prescription. It’s taken after unprotected sex or if your usual birth control fails (such as when a condom breaks). It’s up to 89 percent effective when taken within three days (72 hours) after unprotected sex, and the sooner you take it, the better. Plan B contains levonorgestrel, a synthetic hormone that delays or prevents ovulation.
“Ovulation is the release of an egg by the ovary, and so by definition, [Plan B prevents] the release of an egg, preventing fertilization of that egg by sperm,” Dr. Jonas Swartz, OB-GYN and associate professor at Duke University, tells PGN.
Plan B isn’t the only emergency contraception option
Other kinds of emergency contraception are:
- Ulipristal acetate (sold as ella): Available by prescription, ella can be taken up to five days (120 hours) after unprotected sex. Research suggests it’s more effective than Plan B and may work better for people who weigh between 165 and 194 pounds.
- Intrauterine devices: Three types of IUDs—the copper IUD (Paragard) and two hormonal IUDs (Liletta and Mirena)—can be used as emergency contraception if inserted within five days after unprotected sex. IUDs are the most effective form of emergency contraception, preventing more than 99.9 percent of pregnancies when used this way.
Is it normal to have heavier menstrual bleeding after taking Plan B?
Yes. Some people may experience heavier menstrual bleeding after taking Plan B, “but it usually goes away,” explains Swartz.
Some people may also notice spotting shortly after taking Plan B or in the days leading up to their next period.
No, Plan B does not cause an abortion
One of the most common myths online is that Plan B causes an abortion. It does not.
Emergency contraception works by delaying or preventing ovulation, which helps prevent pregnancy before it begins. It does not end an existing pregnancy.
“We don’t use Plan B for abortion; we use mifepristone,” Dr. Aileen Gariepy, OB-GYN and director of complex family planning at Weill Cornell Medicine, tells PGN. She explains that if anything, the hormone in Plan B would support an ongoing pregnancy rather than cause an abortion.
No, emergency contraception does not cause infertility or cancer
Despite false claims circulating online, there is no evidence that Plan B or other forms of emergency contraception cause infertility or cancer.
Is Plan B less effective depending on your weight?
Yes, research suggests that Plan B may be less effective for people who weigh 165 pounds or more.
“It has to do with the body mass index (BMI) … if they’re in the criteria of what is categorized as overweight or obese, they would be better off getting a prescription of ulipristal acetate [ella] than relying on Plan B, if they can,” Gariepy adds. “But if they can’t get ulipristal acetate, I would still take Plan B if I didn’t want to be pregnant and that’s what I had access to.”
Can I take Plan B while taking a GLP-1?
Researchers are still studying how GLP-1 medications—including Ozempic, Wegovy, Zepbound, and Mounjaro—may affect emergency contraception.
Swartz says current evidence suggests that tirzepatide (sold as Zepbound and Mounjaro) “makes oral contraception, and likely Plan B, less effective, but other GLP-1s don’t appear to have that effect on oral contraceptives or emergency contraceptives.”
If you’re taking tirzepatide and need emergency contraception, Swartz says another option, such as a copper IUD, may be worth discussing with your health care provider.
Overall, experts say the concern isn’t about safety—it’s about whether oral contraception works as well while taking certain medications.
Can I take Plan B if I’m taking regular hormonal contraception?
Yes. If you’ve missed birth control pills or haven’t been taking them consistently and have unprotected sex, taking Plan B may help reduce the risk of pregnancy.
However, if you’re taking your birth control pills correctly every day, emergency contraception usually isn’t necessary.
If you’re prescribed ella, wait at least five days before restarting hormonal birth control because ella can interact with hormonal contraceptives. It is also recommended that you use another method, like condoms, until your next period.
If you have more questions about your regular hormonal birth control and emergency contraceptives, ask your health care provider. The Centers for Disease Control and Prevention also offers guidance on how to use different contraceptive methods together.
What happens if I take Plan B more than once in a month?
Taking Plan B more than once in the same month is not known to cause long-term health problems. However, it isn’t recommended as a regular birth control method because it’s less effective—and often more expensive—than ongoing contraception.
Instead, Gariepy says people who need emergency contraception repeatedly may want to consider switching to Opill, a daily birth control pill that doesn’t need a prescription. “It would be more effective at preventing pregnancy throughout a cycle than taking multiple doses of Plan B,” she says.
For more information, talk to your health care provider.