Plan B One-Step® is a single pill you take by mouth. It must be taken within 72 hours (3 days) after unprotected sex or birth control failure to help prevent pregnancy. The sooner you take it, the better it works.


You will know Plan B One-Step® worked when you get your next period, which should come at the expected time, or within a week of the expected time. If your period is more than a week late, it is possible you may be pregnant. You should get a pregnancy test and follow up with your healthcare provider.

Keep in mind, Plan B One-Step® is less likely to work if:
  • You've already had unprotected sex or birth control failure earlier in your menstrual cycle, as you may already be pregnant
  • You have unprotected sex or birth control failure again in the same menstrual cycle after taking Plan B One-Step®, because it only protects against one incident of unprotected sex or birth control failure
  • You vomit within 2 hours of taking Plan B One-Step®—talk to a healthcare provider to find out if you should repeat the dose

If you experience severe abdominal pain, you may have an ectopic (outside the uterus) pregnancy and should get immediate medical attention.


If you're sexually active, it's always a good idea to see a healthcare provider for routine checkups. Your healthcare provider will discuss your birth control options and answer any questions you may have. Your healthcare provider can also talk to you about sexually transmitted diseases (STDs) and, if necessary, test you for them.

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