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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. 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
  • 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 professional.

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

Are there any drug interactions?

Examples of drugs or herbal products that could decrease the effectiveness of Plan B One-Step include barbiturates, bosentan, carbamazepine, felbamate, griseofulvin, oxacarbazepine, phenytoin, rifampin, St John's wort, topiramate, and certain HIV/AIDS medications.

Contact your healthcare professional before taking Plan B One-Step if you have any concerns or are taking any of these medications.

Fertility after taking Plan B One-Step

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

Things to consider

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

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