How long can plan b delay your period if tooken 3 days after finishing your period?

Plan B effect : Plan b is essentially taking a high dose of birth control to disrupt the hormonal patterns in your body to delay or present ovulation. An abnormal period afterwards is not surprising. A pregnancy test should be done 14 days after plan b. See your doctor for a better birth control plan. You would expect a cycle around the usual time but irregular bleeding may occur.