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Ask Dr. Norm S. Your Own Question
Dr. Norm S.
Dr. Norm S., Board Certified OB/GYN
Category: OB GYN
Satisfied Customers: 11252
Experience:  Over 30 years of experience in OB/GYN practice, including teaching students. Fellow of American Board of Obstetrics and Gynecology.
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How far is Plan B effective after ovulation?

Customer Question

I have a question regarding Plan B. I had unprotected sex on the evening of the 17th. Im pretty sure I ovulated today. I took a Plan B this morning. If I take another one now will this be more effective? I have heard that Plan B will not work if you have ovulated already.
Submitted: 2 years ago.
Category: OB GYN
Expert:  Dr. Norm S. replied 2 years ago.

The scientific literature is somewhat confusing as to how effective Plan B is if taken after ovulation. I believe that it's still effective. Effectiveness decreases the longer after intercourse that Plan B is taken. It is most effective taken within 24 hours, but is effective up to 5 days after intercourse.

Plan B is normally taken once and then repeated 12 hours later, so I would definitely do that. If you took Plan B One Step, it's not necessary to repeat it, and there is no evidence that it would be more effective doing so.