How effective is that plan b morning pill? within how many hours am i suppose to take the pill in order for it to work?

Within 72 hours: Plan b (levonorgestrel)should be taken within 72 hours (preferably within 12-24 hours) of unprotected sex. If vomiting occurs within 2 hours of taking Plan B one step repeat the dose.Some side effects are abdominal pain/cramps/nausea/breast tenderness, spotting/dizziness. Plan b is not used routinely to prevent pregnancy, discuss birth control options with your doctor.Practice safe sex use condoms.