It is best not to mix formula and breast milk during the same feeding, but you can mix them during the same day. In case of sufficient breast milk, babies from 0-6 months should be exclusively breastfed, and after 6 months, babies need to increase complementary foods with appropriate formula feeding. The process of feeding with formula, first let the baby eat breast milk, both sides of the breast milk are all eaten after still not full, you can only let the baby eat a small amount of formula again. However, it is easy to show the baby’s indigestion. If the baby is full after both sides of the breast are sucked, but there is not enough milk secretion in the breast by the next feeding, you should use formula instead of breastfeeding once.