Your Guide To Switching Baby Formula

Expert Reviewed

Amy Peterson is an international board certified lactation consultant and retired La Leche Leage leader based in Idaho.
Amy Peterson, B.S., I.B.C.L.C. Motherhood / Parenting
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Sometimes, the baby formula you start with isn’t the one you stick with. While all baby formulas marketed and sold in the United States must meet the same federal nutrient standards, ingredients differ. Learn some reasons pediatricians recommend and parents choose to switch, plus a guide to making the transition from one formula to another easy on your baby.

6 Signs You Might Need to Switch Baby Formulas

Parents should start their babies on a standard milk-based formula unless they have a medical condition, such as an allergy to cow’s milk, that warrants the use of a specialized variety, says Jessica Gust, a pediatric dietitian and founder of Element Nutrition Co. for Kids in Arroyo Grande, California.

If their baby isn’t tolerating a standard formula, the best formula to change to depends on the symptoms, she says. There are several potential signs a baby isn’t tolerating their current formula well.

Excessive Spit Up

All babies spit up due to their underdeveloped digestive systems. As long as your infant is steadily gaining weight—about 6 ounces a week—and wetting diapers at least once every six hours, there’s often little to worry about. But when spit up amounts to more than 2 tablespoons at each feeding, it could be a sign of a formula intolerance.

Very Slow Weight Gain

Tracking weight gain and diaper output can be useful in gauging a baby’s overall well-being. When infants are gaining weight properly, parents may note the following:

  • Babies reach their birth weight again 10 to 14 days after birth.
  • Between birth and 3 months of age, they gain about 1 ounce a day.
  • By the time they reach 6 months, babies gain .67 ounces a day.

If your baby doesn’t gain weight as expected, discuss it with your child’s pediatrician.

Extra Fussiness Following Feedings

There are countless reasons a baby might spiral into a crying fit, but when your child is inconsolable during or following a feeding, formula intolerance may be the culprit. A study of 256 babies between 1 and 3 months old who were prone to excessive crying and fussiness reported a “substantial decrease” in symptoms following a 14-day switch from a standard milk-based formula to a partially hydrolyzed 100% whey or whey-enriched protein formula.

Bloody Stool

There’s no way around it—finding blood in your baby’s diaper can be a scary sight. While there are several reasons for bloody stools—all of which necessitate a call to your pediatrician—one culprit may be an allergy to cow’s milk, which is the protein source for standard baby formulas.

Severe Constipation

Formula-fed babies generally have at least one bowel movement a day, though going up to two days without one is no cause for concern.

However, if your baby is straining, producing hard, small stools, or suffering from painful stomach cramps, it’s likely they’re constipated. A diet change could provide some relief. Babies who use a formula without palm oil may have softer stools.

Be aware that switching to a low-iron formula in an effort to ease constipation isn’t recommended. Infants require iron intake for proper growth and development, and the amount present in baby formulas shouldn’t cause constipation.

Allergy Symptoms

An estimated 2% to 3% of babies develop a milk allergy within their first few months (though most outgrow it). They can show symptoms either immediately following a feeding or up to 10 days later. These symptoms include:

  • Eczema or skin rashes
  • Loose stools (which may contain blood)
  • Vomiting or gagging
  • Refusing bottles
  • Fussiness
  • Wheezing
  • Swelling
  • Hives
  • Anaphylactic shock (though more common with other food allergies)

If your baby experiences any of these symptoms of an allergic reaction, contact your pediatrician.

The Best Method for Switching Formulas

If you suspect your formula-fed infant is struggling with an intolerance, you may consider trying something new. Follow these steps for a successful formula change.

Consult Your Baby’s Pediatrician

While parents know their babies best, a recent BioMed Central report found they often confuse normal infant behavior for allergies or intolerances, switching formulas to little benefit. The study underscored the importance of consulting your child’s pediatrician before making any dietary changes.

Consider Each Formula’s Protein Type

There are four main types of baby formula. Talk to your pediatrician about which makes sense for your baby.

  • Milk-based: This standard formula contains intact cow’s milk proteins casein and whey. Cow’s milk proteins are larger than human milk proteins (breast milk) and can be difficult for some babies to digest. Some milk-based formulas have added whey to make the casein-whey ratio more similar to breast milk, thus easier to digest.
  • Partially or fully hydrolyzed: Rather than fully intact, the milk proteins in this formula are broken into smaller pieces. Some types include 100% whey protein while others are a casein-whey blend with added whey. Hydrolyzed formulas are often recommended for babies with a family history of eczema and for babies with reflux symptoms.
  • Extensively hydrolyzed: Often referred to as “predigested” or “hypoallergenic,” the milk proteins in this formula are almost entirely broken down or removed completely (free amino acid-based). It may be recommended for infants allergic to cow’s milk.
  • Soy-based: Because milk and soy allergies often go hand in hand, soy formulas are not recommended for babies who can’t tolerate dairy. According to the American Academy of Pediatrics (AAP), there are few circumstances in which soy formula should be chosen instead of milk–based formula.

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Transition Properly

There are two accepted methods for switching formulas, says Amber Rodenas, a pediatric dietitian in Harker Heights, Texas.

  • One-step transition: If your baby switches from a standard formula to one made to be easier to digest, such as a hydrolyzed option, no transition time is necessary. “There should be few side effects,” Rodenas says. “However, monitoring changes in the baby’s bowel movements or other signs of tolerance is still recommended.”
  • Slow transition: For babies transitioning from a specialized formula, such as a hydrolyzed option, a gradual change gives parents time to monitor side effects. This method requires mixing the two formulas together, decreasing the amount of the original formula incrementally.

Because the formula aisle is enough to make any sleep-deprived parent’s brain hurt, we analyzed the price and nutritional components of more than 80 baby formulas to determine the best products. Product details and pricing are accurate as of the publication date. See how popular baby formulas stack up in our list of the Best Baby Formula 2021.

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On Bobbie's Website


Questions & answers for consumers concerning infant formula. U.S. Food and Drug Administration. Accessed 4/24/2021.

Spitting up in babies. Accessed 4/24/2021.

Spitting up self-care. Medline Plus. Accessed 4/25/2021.

Slow weight gain in infants and children. Boston Children’s Hospital. Accessed 4/25/2021.

Formula feeding faqs: some common concerns. Kids Health. Accessed 4/25/2021.

Vivatvakin B, Estorninos E, Lien R, et al. Clinical response to two formulas in infants with parent-reported signs of formula intolerance: a multi-country, double-blind, randomized trial. SAGE Journals. 2020.

Infant constipation. Accessed 5/8/2021.

Stool — blood in. Seattle Children. Accessed 4/24/2021.

Dehghani S-M, Ahmadpour B, Haghighat M, et al. The role of cow’s milk allergy in pediatric chronic constipation: a randomized trial. Iranian Journal of Pediatrics. 2012.

Constipation: infant. Nationwide Children. Accessed 4/26/2021.

Patient education: Constipation in infants and children (beyond the basics). UpToDate. Accessed 5/7/2021.

Choosing an infant formula. Accessed 5/25/2021.

Anxious parents misdiagnose milk formula intolerance. ScienceDaily. Accessed 4/25/2021.

Sauser J, Nutten S, de Groot N, et al. Partially hydrolyzed whey infant formula: Literature review on effects on growth and the risk of developing atopic dermatitis in infants from the general population. Int Arch Allergy Immunol. 2018;177(2):123-134.

Meyer R, Foong RX M, Thapar N, Kritas S, Shah N. Systematic review of the impact of feed protein type and degree of hydrolysis on gastric emptying in children. BMC Gastroenterol. 2015;15:137.

Padial-Jaudenes M, Castanys-Munoz E, Ramirez M, Lasekan J. Physiological impact of palm olein or palm oil in infant formulas: A review of clinical evidence. Nutrients. 2020;12(12):3676.

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