When is the right time to take a pregnancy test after taking plan b?

Pregnancy test: Home pregnancy tests can be positive as soon as the first day of your missed period. Plan B is an emergency contraceptive that uses high doses of hormones to prevent implantation of the fertilized embryo in the uterus. It typically causes irregular bleeding, nausea, breast tenderness, and other side effects. You should consult a Dr for regular contraceptive options ASAP.