Breastfeeding increases the bond between mother and baby, and breast milk contains many natural immunoglobulins that strengthen the baby’s immune system, making it the best way to feed the baby. There are numerous studies showing that taking levothyroxine sodium ( L-T4 ) during pregnancy and breastfeeding has no significant effect on pregnant women and infants, so it is possible for hypothyroid patients to breastfeed. However, it is recommended that hypothyroid patients should take physiologic doses of thyroxine replacement therapy during pregnancy and postpartum to maintain normal thyroid function, review regularly, and ensure accurate drug doses.