When used as directed, Plan B One-Step® is generally safe and effective. Plan B One-Step® contains levonorgestrel, the same hormone used in many birth control pills, just at a higher dose. But it shouldn't be used as regular birth control, because it's not as effective.

Some women may experience side effects, which may include:

  • A period that is lighter, heavier, early, or late
  • A period that is lighter, heavier, early,
    or late
  • Nausea
  • Lower abdominal cramps
  • Tiredness
  • Headache
  • Dizziness
  • Breast tenderness
  • Vomiting

Some women taking Plan B One-Step® may have changes in their period such as spotting or bleeding before their next period. If your period is more than a week late, you should get a pregnancy test and follow up with your healthcare provider.

If you vomit within 2 hours of taking the medication, call 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.

Fertility After Taking Plan B One-Step®

A rapid return of fertility is likely after taking Plan B One-Step® for emergency contraception; therefore, you should resume your regular method of birth control—or start one, if you don't have a regular method—right away, since Plan B One-Step® does not protect against additional acts of unprotected sex.

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