The Human chorionic gonadotropin test is done to check for the hormone hCG in blood or urine of a woman. This test can be used to check the exact amount of the hormone or whether it is present or not. In general, the blood test happens to be more sensitive to the hCG hormone and can be done two days before a woman would expect her period to start. Urine tests may show a falsely negative test, which may lead to repeated testing if the suspicion of pregnancy remains.