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Dr. K.
Dr. K., MD
Category: OB GYN
Satisfied Customers: 3948
Experience:  Board certified OB/GYN with 20 years of experience.
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I just took plan on Sunday as a precaution after having

Customer Question

Hi, I just took plan b on Sunday as a precaution after having unprotected sex. I had a mishap with a condom last night (monday) and was wondering if it would be safe for me to take plan b again a day or two after I took it the last time? The first day of my last period was 11/15 or 16, and my periods are fairly regular (every 28ish days)...I read that plan b's half-life is 24-36 hours, so was it still in my system last evening? I feel like the chances are probably slim that I could get pregnant right now, but I just wanted to make sure.
Submitted: 1 year ago.
Category: OB GYN
Expert:  khagihara replied 1 year ago.

You can take plan b again.

Expert:  Dr. K. replied 1 year ago.

Plan B is effective if taken within 72 hours of intercourse. It is most effective when taken within 24 hours after unprotected intercourse. It does not matter what the half life is, or how long it is in your system. It is the timing that is important. You can take another Plan B. It is likely that the one you took Sunday is already working but it is not harmful to take another. You need to use condoms the rest of the month as you will not want to keep taking Plan B. When you get your period, be sure to start a reliable form of birth control

Customer: replied 1 year ago.
Thanks for your reply! So there won't be any adverse side effects with the plan b again? I tend to get migraine headaches so I don't take birth control with estrogen...I know that plan be is just progesterone...so it should be fine as far as my headaches, etc? If I take it tomorrow (after the mishap last night) that's still enough time for it to take effect?
Expert:  Dr. K. replied 1 year ago.

The adverse effects mainly center around abnormal bleeding and irregular bleeding. You cannot expect the cycle to to be normal. It is ok to take it in the first 72 hours after unprotected sex but it is most effective if taken within 24 hours. So it would be better to take it tonight.