Slowly increase the amount of the new formula over time. Try slowly introducing small amounts of the new formula by mixing it with your regular formula.Keep in mind that your baby may seem to not like the taste, or may have a hard time tolerating a different formula, initially. Most babies will do just fine with different brands of formula, including store brands, as long as they're the same type, like cow's milk-based, soy, hypoallergenic (extensively hydrolyzed), or elemental (amino acid-based). Talk with your pediatrcian or other health care provider if you are having difficulty breastfeeding or finding infant formula. Note: Children younger than 6 months old should only drink breast milk or infant formula.