Regarding how long to take the pill, it should be analyzed on a case-by-case basis, because the pill has a long-acting, medium-acting, and short-acting, as follows: 1, long-acting contraceptive pills: the duration of a longer period of time, probably can last 3-4 days, in the 3-4 days before sex can achieve the purpose of contraception, and the human body is still relatively small damage. 2, medium-acting contraceptive pills: the duration of the effective time of about 2-3 days, in the sex before 2-3 days to eat can play the purpose of contraception. 3, short-acting contraceptive pills: duration of about 24 hours, in the sex before about 24 hours to eat. The short-acting contraceptive pill: the duration is about 24 hours, about 24 hours before sex can be eaten. 4, emergency contraceptive pills: during sex or 1-2 hours after sex can also play the purpose of contraception, but the harm to the body is relatively large.