Evening Pill Emergency Contraceptive Pill is an emergency birth control pill. It provides a safe and effective way to prevent an unintended pregnancy after unprotected sex or contraceptive failure. However, it should not be used as regular contraception. It works to prevent pregnancy by temporarily stopping the release of an egg from the ovary or by preventing fertilization (union) of the egg by sperm. It comes as a single dose and can be taken with or without food. Evening Pill Emergency Contraceptive Pill is usually effective if taken within 72 hours of unprotected sex. The most common side effects of this medicine include headache, nausea, lower abdominal pain, and fatigue. The patient may also experience dizziness, diarrhea, vomiting, breast tenderness, and irregular period for the next cycle. If these bother you or appear serious, let your doctor know. There may be ways of reducing or preventing them. Before taking this medicine, check if you are not pregnant already or it is being more than 5 days you miss your period or its already 72 hours of unprotected sex. Inform your doctor if you are breastfeeding. It is generally advisable to perform a pregnancy test after 5 days of medicine usage, to make sure medicine works properly.