The pill needs to be taken within a certain period of time in order to have a better contraceptive effect, and the time of taking different contraceptives is different. 1. Short-acting contraceptive pill: start taking it on the 5th day of menstruation and take it for 21 days continuously. It is recommended to take it at a fixed time every day, preferably at night before going to bed, so as to reduce the stimulation of the gastrointestinal tract and dizziness due to oral short-acting contraceptives. If a day is missed, taking it on the second day will still be effective. But if suffering from uterine fibroids, thrombotic tendency, hypertension, diabetes, etc., oral short-acting contraceptive pills are not recommended; 2. Emergency contraceptive pills: such as compound levonorgestrel tablets, levonorgestrel tablets, etc., for the remedy after contraceptive failure. Usually taken orally within 72 hours after intercourse. The number of oral emergency contraceptive pills should not exceed two times a year, so as not to affect the body, such as endocrine disorders; 3. Long-acting contraceptive pills: such as Conjugate, medroxyprogesterone acetate, etc., taken orally on the first day of menstruation, and again on the 12th day. Long-acting contraceptives and short-acting contraceptives may cause the endometrium to become thinner, causing a decrease in menstrual flow or even amenorrhea. If amenorrhea occurs, be sure to rule out pregnancy first, as all birth control pills are not 100% effective, and emergency contraceptives may cause withdrawal bleeding after taking them.