A quantitative immunoassay of blood human chorionic gonadotropin (HCG) <3.1ug/l is considered negative for pregnancy, and a blood concentration >25U/L is considered positive for pregnancy. Due to the different reagents used in each hospital, there may be slight differences in the reference values. Generally speaking, about 10 days after intercourse or 3~7 days after regular menstruation delay, accompanied by nausea, vomiting and other early pregnancy reactions, it is recommended to go to the hospital to draw blood to check the human chorionic gonadotropin to determine whether you are pregnant or not. However, ultrasonography is needed to determine whether the pregnancy is intrauterine. In addition, ectopic pregnancy, gestational trophoblastic disease, precocious puberty and tumors may also show elevated HCG.