Read the instructions, warnings and enclosed product leaflet before use. This product works mainly by preventing ovulation (egg release). It may also prevent fertilization of a released egg (joining of sperm and egg) or attachment of a fertilized egg to the uterus (implantation). Do not use if carton is open or tear strip is removed or blister seal is broken or missing. Reduces chance of pregnancy after unprotected sex. One tablet. One step. The sooner you take it, the more effective it will be.