I took a plan b & my period is 4 days late ?

Cycle is irregular: The Plan B pill can make your cycle irregular,it does NOT mean it is not effective. Plan B can work in one of three ways depending on where you are in your cycle. It can prevent or delay ovulation, can interfere with the fertilization of the egg or may prevent implantation by altering the lining of the uterus. If you take Plan B One-Step within 24 hours, it is about 95% effective.

Take HPT if > 7 days: late. 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.