Due to the different types of drugs as well as different dosages, the actual time to take in advance will also vary, usually short-acting birth control pills, progesterone and other drugs need to be taken about 15 days before the onset of menstruation. Delay the onset of menstruation of drugs generally refers to hormone drugs, its effect on the body will play a certain role in regulating, so as to change the time of menstruation, such as short-acting contraceptive pills, progesterone, etc., the drug often need to be taken in the next menstrual period 15 days or so before the onset of menstruation, in the menstruation of the right period to stop using the drug, the general stopping of the drug can be around 1 week to the onset of menstruation. Due to the different types of drugs, the patient’s physical condition is different, the choice of drugs will be different, do not self-medication, should be under the guidance of the doctor for reasonable use.