An IUD is highly effective and works quickly to prevent pregnancy. The copper IUD starts working as soon as it is inserted, providing immediate contraception. This type of IUD creates an environment in the uterus that is hostile to sperm, preventing fertilization. The hormonal IUD also works quickly, but it may take a few days to fully thicken cervical mucus and inhibit ovulation. In most cases, the hormonal IUD is effective immediately if inserted during the first few days of menstruation. If inserted at other times, backup contraception may be recommended for up to 7 days to ensure full effectiveness. The copper IUD provides immediate protection against pregnancy, while the hormonal IUD may take a short period to become fully effective. Once inserted, both types of IUDs offer long-term protection, ranging from 3 to 10 years, depending on the type. Their high effectiveness (over 99%) makes them a reliable choice for long-term contraception. After insertion, there is no need to remember to take a daily pill, making the IUD an appealing option for those seeking a low-maintenance method of birth control.