Can my menstrual cycle change because i took plan b?

Yes: It's common to experience an irregular period after plan-b.

If it occurs, it is: usually temporary. Potential side effects w emergency contraception include: menstrual flow changes (spotting, bleeding, early or late period), nausea, vomiting, dizziness, fatigue, headache, breast tenderness & abdominal pain or cramps. Take pregnancy test & notify dr if your period is 7 or > days late.