Most accurate pregnancy tests
Many home pregnancy tests claim to be 99 percent accurate on the day you miss your period. Although research suggests that some home pregnancy tests don't consistently spot pregnancy this early, home pregnancy tests are considered reliable when used according to package instructions one week after a missed period.
Most medicines should not affect the results of a home pregnancy test (HPT). This includes over-the-counter and prescription medicines, including birth control pills and antibiotics. Only medicines that have the pregnancy hormone hCG in them can give a false positive test result. A false positive is when a test says you are pregnant when you're not. Sometimes medicines containing hCG are used to treat infertility (not being able to get pregnant).
Alcohol and illegal drugs do not affect HPT results. But do not use these substances if you are trying to become pregnant or are sexually active and could become pregnant.