Norethindrone is a form of progesterone, a female hormone. Norethindrone prevents ovulation (the release of an egg from an ovary). This medication also causes changes in your cervical mucus and uterine lining, making it harder for sperm to reach the uterus and harder for a fertilized egg to attach to the uterus. Norethindrone is used for birth control (contraception) to prevent pregnancy. Norethindrone is also used to treat menstrual disorders, endometriosis, or abnormal vaginal bleeding caused by a hormone imbalance. Norethindrone may also be used for other purposes not listed in this medication guide.