Levonorgestrel tablets are emergency contraceptive pills that are taken by female patients and have a 20% failure rate. The efficacy of the pill, which is a prerequisite for success, must be used correctly. After unprotected intercourse or failure of a contraceptive method, it is standard to take the first tablet as soon as possible within 72 hours, and then take the second tablet 12-16 hours after the first one is taken. To be effective and to ensure that pregnancy is avoided, it is important to take the pill as described above. However, there is no such thing as a sure thing. Clinical trials have confirmed that following this method is basically effective for most people, but the probability that individual patients may fail cannot be ruled out. Patients who doubt the efficacy of the drug can promptly go to the hospital to determine, under the guidance of a doctor, whether further measures are needed.