After taking Plan B, the recommended time to take a pregnancy test is 3-4 weeks later, as this is when most pregnancy tests can accurately detect the pregnancy hormone. However, if you experience symptoms of pregnancy, such as nausea, breast tenderness, or fatigue, you should take a pregnancy test sooner. If the test is negative, you may want to take another test a few days later to confirm the result. It’s important to remember that Plan B is not 100% effective, so it’s still possible to get pregnant even after taking it.