This is a backup plan that helps prevent pregnancy from happening after unprotected sex or birth control failure. It is not for routine use! Plan B One-Step® should be taken within 72 hours (3 days) after you've had
unprotected sex or birth control failure to help prevent pregnancy from
happening. The sooner you take it, the better it works. If you vomit
within 2 hours of taking the medicine, you should contact your
healthcare professional to seek information if you should take another
dosage. This pill contains levonorgestrel, the same ingredient used in many birth control pills - and it works in a similar way.