You can usually take a pregnancy test about 2 to 3 weeks after unprotected sex. Most home tests are most accurate from the first day of a missed period, when hormone levels are high enough to detect reliably.
After fertilization, the body starts producing a hormone called hCG, but it takes time to build up. This hormone typically appears in the body several days after implantation, which itself happens about a week after fertilization. Because of this delay, testing too early can lead to a false negative even if pregnancy has occurred.
If you are unsure when your next period is due, a more reliable approach is to wait at least 21 days after unprotected sex before testing. Some early-detection tests may work a few days before a missed period, but they are less dependable at that stage.
If your test is negative but your period still does not come, repeat the test a few days later. For ongoing uncertainty or symptoms like pain or unusual bleeding, it is important to speak with a healthcare provider for proper evaluation.