Which Emergency Contraception Is Right for You?

Between the two pills, ella (ulipristal) is more effective than Plan B (levonorgestrel), works further out, up to 5 days versus best-within-3, and holds up better at higher body weight. But the single most effective emergency contraception is a copper IUD placed within 5 days, which is over 99% effective regardless of weight and doubles as long-term birth control. Whatever you choose, sooner is better.

Body weight affects the pills. Plan B (levonorgestrel) becomes less effective above roughly 165 lb, and ella (ulipristal) is more effective across the board and works up to about 195 lb or a BMI of 35 before its effectiveness falls too. Above that, the copper IUD is the reliable choice because it isn't affected by weight at all. This is exactly why the tool asks about weight: not to judge, but to point you to what will actually work.

Sooner is always better, but the windows are: Plan B works best within 72 hours (3 days); ella works up to 120 hours (5 days); and a copper IUD can be placed up to 5 days after sex. After 5 days, these options are no longer reliable: take a pregnancy test about 3 weeks later or if your period is late, and talk to a provider about your options.

No. Emergency contraception stops pregnancy from starting: the pills (Plan B, ella) mainly by delaying ovulation, a copper IUD by blocking fertilization. It does not end an existing pregnancy and will not work if you're already pregnant. It's different from mifepristone/misoprostol (the abortion pill). EC is safe, and you can't harm an existing pregnancy by taking it.

Yes: emergency contraception prevents pregnancy, but does nothing about STIs. If the sex was unprotected, plan to test at the right time for each infection (and if there's any HIV-exposure risk, PEP is a separate 72-hour clock). Use our test-window tool for timing and the finder to get tested; this tool covers only the pregnancy side.

No. This is general educational information to help you understand the emergency-contraception options and act quickly: it can't account for your full medical history or current medications (for example, some medicines interact with ella). A pharmacist can help you get EC today, and a clinician can place a copper IUD; reach out to one to confirm the best choice for you.