Plan B emergency contraception should NOT be taken by women with a confirmed or suspected pregnancy, undiagnosed abnormal vaginal bleeding, an allergy to any component of the product, or any of the following conditions: blood clotting disorder, heart attack, stroke, thrombophlebitis, impaired liver function, breast cancer, or any cancer involving the reproductive organs. Women who are breastfeeding should stop for 24 hours after taking Plan B contraception.
Plan B is intended to prevent pregnancy in the case of an emergency, and Plan B will not protect from HIV or other sexually transmitted diseases and infections.