How long can plan b symptoms last after taking it?

Usually just a day: or two. But symptoms of nausea, abdominal pain, fatigue, headaches. dizziness and breast tenderness can last up to a week or even longer. Unexpected vaginal bleeding may be one of the side effects, and this may last up until your period starts. Plan B may also cause your next period to be heavier or lighter than usual, or to come earlier or later than normal. If no period in 3 weeks, do preg test.