how effective is a plan b

Plan B (levonorgestrel) emergency contraception is estimated to be between 60% to 94% effective at preventing pregnancy when taken within 72 hours (3 days) after unprotected sex, with higher effectiveness the sooner it is taken. Some sources specify it reduces the chance of pregnancy by up to 89% if taken within this time frame. Taking the pill within 24 hours increases its effectiveness even more. The effectiveness decreases over time but some studies suggest it can be moderately effective up to 5 days after intercourse. Plan B works primarily by delaying ovulation and is most effective before ovulation occurs. If ovulation has already happened, Plan B becomes much less effective or ineffective. The pill is meant as emergency contraception and is less effective than regular birth control methods. There is no official weight limit, but some evidence suggests it may be less effective for people weighing 165 pounds or more, though it still offers some benefit. In summary, Plan B is a valuable emergency measure to reduce the risk of pregnancy after unprotected sex but should be taken as soon as possible for best results and is not meant for routine birth control use.