The earliest you can take a pregnancy test depends on the type of test you use. Home pregnancy tests that detect the presence of the hormone human chorionic gonadotropin (hCG) in your urine are the most common type of test.

Most home pregnancy tests can detect hCG in your urine about 10-14 days after fertilization, which is around the time of your expected period. However, some tests are more sensitive and can detect hCG even earlier, as early as 7-10 days after fertilization.

It's important to read the instructions on the pregnancy test you're using carefully to know the earliest time you can take the test for accurate results. Additionally, taking the test too early can result in a false negative result, so it's best to wait until you've missed your period to increase the accuracy of the test.