Emergency contraceptive pills often refer to a class of drugs that achieve contraceptive effect by stopping or delaying the release of egg cells, and the most common ones at present are levonorgestrel-type drugs. If there is late menstruation after taking emergency contraceptive pills, it may be caused by two situations: 1. Contraceptive failure: emergency contraceptive pills have a certain efficiency, but the possibility of contraceptive failure may also occur after taking the drug, or emergency contraceptive pills taken outside the effective contraceptive time without taking the drug according to the instructions may also cause contraceptive failure. So if the period is late, you can use the early pregnancy test paper to detect whether you are pregnant; 2, drug side effects: emergency contraceptive pills will have a certain effect on ovulation in addition to the endometrium, which may lead to delayed menstruation, often belonging to the side effects of the drug. In addition, there may be side effects such as stomach discomfort, headache, dizziness or a small amount of vaginal bleeding after taking the emergency contraceptive pill, which usually do not require special treatment. If a patient’s period is delayed for too long, it is recommended that the patient seek medical attention to identify the cause and treat it as soon as possible. Although the emergency contraceptive pill has a certain contraceptive effect, it may have certain effects on women’s body, so patients are advised to use more effective contraceptive methods, such as condoms, which can also play a role in preventing the spread of STDs.