HCG test is to test the level of human chorionic gonadotropin in the blood by drawing peripheral venous blood. Fasting is not required, and the hormone level does not have any relationship with diet, drinking, sleeping, etc., but the test is limited by time. HCG clinically starts to secrete on the 6th day after fertilization, and can be detected by blood test on the 7th day. However, pregnancy is not immediate after coitus, and it is impossible to determine the time of fertilization, and the sperms survive for 2-3 days. Therefore, it is generally recommended to go to the hospital to check the blood HCG after 10 days of coitus in order to be effective, and the test will be falsely negative if it is done too early. After intercourse, you can determine whether you are pregnant or not by the elevated blood HCG, and how the embryo develops in the early stages of pregnancy is also reflected by this value. In the early stages of pregnancy, when the embryo cannot be seen by ultrasound, if the blood HCG doubles every other day, it suggests that the embryo is developing well; if the blood HCG grows slowly every other day in the early stages of the pregnancy or decreases, it generally suggests that there is a possibility of preterm miscarriage or ectopic pregnancy, and the doctor indirectly determines the development of the embryo through the laboratory tests of HCG and progesterone. HCG plays a very important role in clinical practice. If you have menopause, abdominal pain or irregular bleeding, you can go to the hospital for a timely checkup without waiting for fasting, and the result can be out very soon, with a very high accuracy rate.