Plan B (also known as the morning-after pill) is an emergency contraception pill that is used after unprotected sex to prevent pregnancy. Plan B works in one of three ways:

  1. Stopping the ovary from releasing an egg.
  2. However, if this has already happened, it may prevent fertilization of the egg.
  3. But if fertilization has already occurred, then it may prevent attachment of the fertilized egg to the wall of the uterus.

On the other hand, if fertilization and attachment have already happened prior to taking Plan B, the pregnancy will continue. It’s important to note that Plan B will not terminate an already attached, fertilized egg, and it is not the same thing as the abortion pill (also known as RU-486 or Plan C).

According to doctors and other healthcare professionals, Plan B should not be used as a regular form of birth control because it is simply not as effective as other methods. For instance, Plan B, if taken within 3 days post sexual intercourse, only has an 75-89% success rate. Furthermore, frequent use of Plan B can also cause periods to become irregular, which makes predicting ovulation (when the ovary releases the egg) unreliable. Plus, Plan B does not protect against sexually transmitted diseases. Finally, if you weigh more than 155lbs, Plan B may not work as effectively according to some studies.

There are many other methods to prevent pregnancy than can be considered. Ask your doctor about different forms of pregnancy prevention and which option may be best for you. As always, when taking any medication, be sure to ask about possible interactions with other medications you might be on.

Also, it’s important to know that if you’ve taken Plan B, your next period may be abnormal. For example, it might be heavier, lighter, earlier, or later than your normal cycle. If you are concerned you may be pregnant, Focus Women’s Center offers free pregnancy testing. Call or text 815-322-1585 to schedule an appointment with a nurse and find out for sure.



Hitti, M. (2022). Plan B One-Step: Seven questions and answers. Retrieved from https://www.webmd.com/sex/birth-control/features/plan-b-11-questions-11-answers

Leonard, J. (2020). How many times can you take Plan B (morning-after pill)? Retrieved from https://www.medicalnewstoday.com/articles/how-many-times-can-you-take-plan-b

Villines, Z. (2021) Is there a Plan B weight limit? Retrieved from https://www.medicalnewstoday.com/articles/plan-b-weight-limit