Transitioning from formula to breast milk may cause diarrhea. Breastfeeding diarrhea can occur when a formula-fed infant transitions to breastfeeding due to the infant’s imperfect digestive function and the sudden switch to breastmilk. Usually, the diarrhea can be recovered after a period of adjustment. If the diarrhea is caused by bacterial infection due to lack of attention to nipple hygiene, medication such as cefixime granules may be needed for recovery. The transition from formula feeding to breastfeeding should be gradual to avoid breastfeeding diarrhea. You can alternate formula feeding with breastfeeding, and gradually adjust the proportion of breastfeeding until exclusive breastfeeding. Mothers should also pay attention to personal hygiene when feeding. For problems related to the conversion of formula milk to breastfeeding, it is recommended to consult a doctor for guidance.