Can you tell if it's an ectopic pregnancy by taking blood?

Blood test is mainly to check the serum level of human chorionic gonadotropin, can judge whether there is pregnancy through the level of human chorionic gonadotropin, if only do blood test and can not diagnose ectopic pregnancy, because in the early stages of pregnancy, hormone level is relatively low, this time can not distinguish between normal intrauterine pregnancy or ectopic pregnancy.