Switching formulas

If your formula-fed baby is constipated, throwing up a lot, or gassy, you might be wondering whether it’s time to switch formulas. Occasionally, babies will need a different formula or type of formula, but there are also many instances where baby’s symptoms are quite common and normal. And it can potentially upset your little guy’s belly even more if you frequently switch formulas!

Mother with baby bottle and scoop preparing infant formula milk

The First Month

Gassiness and spitting up is normal in newborns across the board, and while there are individual variations, for the most part it’s due to an immature digestive system. It’s normal for babies to strain and turn a little red when having a bowel movement, even when passing watery breast milk stool.

Constipation (infrequent and hard bowel movements) is common in formula-fed babies in the first month or so, and is usually due to the large amount of iron in most formulas. It typically resolves after 4-6 weeks of age. Gently pulling and pushing baby’s legs in and out, bicycling her legs, and light belly massage can all help to get things moving. Speak with baby’s doctor if the constipation isn’t getting better or stools are bloody, or if you have any other concerns.

Beyond the First Month

Spit up and gassiness continue to be normal. Once solid foods are introduced, you will see further changes in baby’s bowel habits.

Red Flags that baby may not be tolerating their current formula:

  • Eczema
  • Typical allergy symptoms such as wheezing, hives, excessive vomiting.
  • Bloody diarrhea
  • Severe constipation
  • Excessive fussiness after eating
  • Failure to thrive

Most of the time allergy or intolerance issues are due to the milk or soy proteins present in cow’s milk and soy-based formulas, although other ingredients could be the culprit. It’s rare for a baby to be lactose intolerant.

When to switch formulas

It’s always important to consult with baby’s pediatrician when you feel that you need to switch baby’s formula. If an allergy or significant intolerance is suspected, soy formula is often bypassed for a partially hydrolyzed formula or occasionally a different form (concentrate versus powder versus ready-to-feed) or brand. Severe allergies are dealt with using hypoallergenic formulas.

Most of the time parents can switch the formulas without too much protest from baby. If you choose to transition from one formula to another (and as long as it’s not a severe allergy that is causing the switch), you can transition using the pattern below, transitioning to the next step every 1-2 days.

Assuming baby takes 4 oz of formula:

  • 3 oz current formula, 1 oz new formula
  • 2 oz current formula, 1 oz new formula
  • 1 oz current formula, 3 oz new formula
  • 4 oz new formula

In the end, it’s important to recognize what’s normal and what’s a red flag with regard to baby’s digestion. Before considering a formula switch, double-check to make sure you are preparing the formula properly and that you are following baby’s hunger and fullness cues. Sometimes encouraging a full baby to finish their bottle can cause baby to be gassy or to spit up quite a bit. Always work with baby’s doctor to find the best formula for your little one!


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