according to the Mayo Clinic the results are more than 99% accurate MayoClinic the results are more than 99% accurate according to the Mayo Clinic the first day of your missed period testing too early according to the Mayo Clinic wait until you actually miss your period Is a pregnancy test accurate at night, 99 percent Getting pregnant two or three days "Home pregnancy tests: Can you trust the results?" wait one to two weeks are all almost entirely the same level of accuracy according to the Mayo Clinic are pregnancy tests accurate after your missed period pregnancy tests work by detecting the hormone hCG you wait a week after a missed period