After intrauterine device (IUD) insertion, many women experience prolonged menstrual bleeding, which typically occurs in the first few months and gradually normalizes over time. If menstrual bleeding persists after one year of IUD use, it usually indicates the body's difficulty adapting to the device. Post-insertion, the increased local fibrinolytic activity in the endometrium can cause prolonged menstrual bleeding, but this generally resolves quickly. If it persists for a year, we need to rule out other abnormalities. 1. An ultrasound should be performed to check for any displacement or malposition of the IUD. 2. Blood and urine hCG tests should be conducted to exclude pregnancy and ectopic pregnancy. 3. Cervical TCT and HPV tests should be done to rule out cervical lesions, including cervical cancer. 4. If the endometrium appears thickened, a dilation and curettage (D&C) may be necessary to exclude endometrial tumors or even endometrial cancer as causes of the prolonged bleeding. If these abnormalities are ruled out, the prolonged bleeding is generally considered due to the body's difficulty adapting to the IUD. If the condition becomes unbearable, removal of the IUD is usually recommended.