How effective is plan b

• The best time to take Plan B is within 24 hours of unprotected sex.
• Its effectiveness is 85% if taken two days after having unprotected sex and 61% after three days.
• You shouldn't take multiple Plan B pills unless you vomit or have more unprotected sex.

Plan B, commonly known as "the morning-after pill," can effectively prevent you from becoming pregnant, but only if you take it at the right time. 

And while there's no limit to how many times you can take Plan B, that doesn't mean you should treat it like a standard birth control pill that you take regularly. 

How long can you wait to take Plan B?

The sooner you take Plan B after unprotected sex, the better.

"The efficacy of Plan B is the best when you take it within 12 hours, and it goes down from there," says Nichole Butler, MD, board-certified OB-GYN at Weiss Memorial Hospital's Women's Health Center.

You can take Plan B up to 72 hours after unprotected sex.

However, the pill's effectiveness at preventing pregnancy dwindles the later you take it:

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