how long does it take for an iud to work

An IUD's effectiveness and the time it takes to work depend on the type and timing of insertion. Hormonal IUDs take up to 7 days to become effective unless inserted within the first 7 days of the menstrual cycle, in which case they work immediately. Copper IUDs provide immediate protection from pregnancy once inserted, regardless of cycle timing. If a hormonal IUD is inserted at other points in the cycle, backup contraception should be used for one week after insertion for full protection.