Levonorgestrel is an emergency contraceptive used in case of emergency or other contraceptive failure. It is a sex hormone drug that can inhibit the follicles from expelling eggs and affect the fertilization of eggs. It is effective for most female patients, but due to the different physical conditions of each female patient, some patients may experience contraceptive failure, but it is a rare phenomenon and should be noted. If taken for a long time, it may cause irregular vaginal bleeding, menstrual disorders, endocrine disorders, etc. In serious cases, liver and kidney function damage and thrombotic diseases may occur.