It is more accurate to test for pregnancy about 10 days after the HCG injection (human chorionic gonadotropin). After the HCG injection, there may be some confusion with the chorionic gonadotropin produced by the trophoblast cells in a real pregnancy. Therefore, it is recommended to wait for 8 to 10 days after the injection, when the exogenous drug has basically been completely metabolized. A blood test for human chorionic gonadotropin levels at this time may correlate more closely with one’s own pregnancy, and can largely avoid false-positive results due to elevated levels of exogenous human chorionic gonadotropin. It may be advantageous to wait until a normal menstrual period is delayed to have the blood test performed to obtain a more accurate result.