Contraceptive injections are generally long-acting contraceptive injections, available in progestogen-only formulations or in estrogen and progestogen combinations, which have a success rate of more than 98%. It is mainly used for women who have significant gastrointestinal reactions to oral contraceptives. One intramuscular injection is usually given on day 5, and one on day 12 of the menstrual cycle, and another intramuscular injection on days 10-12 of the menstrual cycle. Menstruation usually occurs about 12-16 days after the injection. If progestin-only preparations are injected, often one injection is given every 3 months, but the side effects are more significant and may cause menstrual disorders and even lead to amenorrhea.