Plan B is most effective within 24 hours of unprotected sex, with an effectiveness rate of about 95% to over 97% at preventing pregnancy if taken within that time frame. The effectiveness decreases the longer one waits, dropping to around 61% if taken 48 to 72 hours after sex. Plan B is intended for use within 72 hours, but the sooner it is taken, the better it works, especially before ovulation occurs.
Key Points on Plan B Effectiveness Within 24 Hours:
- Over 95% effective when taken within 24 hours.
- Effectiveness can be as high as over 97% within 24 hours according to some studies.
- It works primarily by delaying or preventing ovulation.
- Effectiveness declines after 24 hours and continues to decrease until 72 hours.
- It is not as effective if ovulation has already happened.
- Plan B is a backup method, not a primary contraception method, so it is best not used regularly.
This information is supported by medical experts and clinical studies from sources such as SingleCare, Drugs.com, Healthline, and official Plan B FAQs.
