The market has plenty of choices for infant formula: cow's-milk based formula, soy formula, organic or non-organic. Choosing the right formula for your baby requires communication with your pediatrician and a bit of trial and error. Depending on why you are changing your baby's formula, you may choose to gradually introduce the new product or you may decide to switch immediately. KidsHealth.org points out that neither method is better than the other. Do what is best for your baby under the guidance of your pediatrician.
Decide whether to switch formula immediately or gradually. You may want to consult with your pediatrician. Although, switching immediately may be the only choice if your infant was allergic to the original formula.
Begin by offering your infant a bottle of the new formula. If you don't notice any signs of allergy including hives, rash, excessive fussiness, bowel habit changes, vomiting or other signs of illness, then you can continue offering the new formula.
Mix one part new formula to three parts of the old formula if you are planning to make a gradual change. If your baby drinks a 4-oz. bottle, use 1 oz. of new formula with 3 ozs. of the old.
Continue offering your baby the same ratio of formula for one or two feedings, or even up to a full day's worth of bottles.
Increase the ratio of new formula to old formula if your baby seems to be doing well. You can offer a bottle of equal parts of each formula for one feeding and then offer one part old formula to three parts of the old if you have not noticed any negative reactions to the milk. Mild gassiness, signs of pain or other signs of illness may mean the new formula isn't working out for your infant.