A pregnancy test before a missed period can detect pregnancy, but the result may be less reliable. Although some sensitive home tests can detect pregnancy early, waiting until after your period is due lowers the chance of a false-negative pregnancy test result.
A positive pregnancy test before a missed period usually means you are pregnant. However, an early negative result does not rule out pregnancy because your body may not yet have produced enough human chorionic gonadotropin (hCG) for the test to detect.
For better accuracy, follow the instructions on the package and use your first urine in the morning, when hCG levels are usually more concentrated. If the result is negative but your period does not start, repeat the test after several days.
For the most reliable results, the FDA recommends taking a home pregnancy test one to two weeks after a missed period. Contact an OB-GYN or another healthcare provider to confirm a positive result or if you continue to get negative results without having your period.