Yes, you can take Plan B while breastfeeding. According to the manufacturer of Plan B One-Step1 , it’s safe to use while nursing and won’t harm your baby. Keep in mind that some cases of reduced milk supply have been reported, but it’s not listed as an official side effect.
Plan B contains a hormone called levonorgestrel. A study published in the journal Contraception has shown that this hormone doesn’t significantly affect the quantity or quality of breast milk.
However, it's important to remember that Plan B is intended as an emergency contraceptive and not for regular use. If you're looking for a consistent birth control method while you're breastfeeding, you should have a conversation with your healthcare provider.