How to switch baby formula

A person holding a baby formula can in a store
Photo credit: Thinkstock

Like so many other baby products, different baby formulas tend to develop their own devoted followers. Once you find one that checks off the right boxes (it's affordable for you, comes in bulk, and hey, your baby likes it!) you probably couldn't be paid enough to voluntarily switch to another brand.

Unfortunately, you might not have much of a choice right now: Formula shortages in the United States have sent parents scrambling to track down their baby's preferred formula brand, and many of those parents have been faced with the task of switching formulas as they come up empty-handed in their quest. (Note: Here's an updated list of available formulas that are in stock online now.)

Advertisement | page continues below

Whatever your reasons for wanting or needing to switch formulas, it might take a little finesse to get your baby on board. There are also a few things to look out for and keep in mind for a smooth transition. Here's what you need to know about making the change.

What kinds of formulas can be switched?

In most cases, it's fine to change formulas, as long as you stick with the same type. For instance, the ingredients in all cow's milk-based, iron-fortified infant formulas (recommended for most babies) are essentially the same.

Likewise, if your baby is on a pediatrician-recommended partially hydrolyzed infant formula (a type of formula given to babies who are sensitive to cow's milk), switching to a different brand of partially hydrolyzed formula won't harm them. But if your baby is on a special type of formula, such as a formula designed for premature babies, and you're considering switching formula types, check with your pediatrician first.

And don't switch from a cow's milk-based formula to an extensively hydrolyzed formula without talking with your pediatrician first, since they may not need to be on that type of formula, which is hard to come by in the shortage.

Formulas made with goat's milk are also becoming more popular. If you're currently feeding your baby cow's milk formula, talk with your pediatrician before giving your baby goat milk formula, which may not be necessary.

How to introduce a new formula

If you're ready to switch your baby to a different formula, it could be as simple as opening up a new can and diving right in (again, assuming you're switching to the same type of formula). Most of the time, you can just stop using your old formula and begin using a new one without any drawn-out transition.

Just because it's safe for your baby to switch formulas cold turkey, though, doesn't mean your baby will like it. The taste may vary slightly – some formulas are sweeter than others, for example, and your baby will probably have gotten used to the flavor of their previous formula. Some formulas are also made with added nutrients, like fatty acids and probiotics, and that can also affect the taste. Switching from a ready-to-feed to a powdered formula, or vice versa, may also take some getting used to.

Advertisement | page continues below

You won't harm your baby by changing brands, but if your baby balks when you switch (by showing a sudden disinterest in this new formula or refusing to finish their bottle) you may be able to introduce them to the new formula gradually rather than all at once.

Can you mix different baby formulas?

Yes, you can mix different baby formulas, as long as one hasn't been recalled and you're preparing it safely in terms of the ratio of formula to water. If you're worried about mixing correctly, try preparing both formulas separately, and then mixing them together after they've been prepared.

If your baby is resisting the switch to a new formula, mixing some of the new in with the old – a little at a time – can help them get used to the change without giving them too big of a surprise at feeding time. Of course, this may not always be possible (for instance, if you've run out of the old formula).

There are different methods when it comes to combining the right amounts of a new and old formula brand. But generally speaking, you can start by mixing two parts old formula and two parts new for a couple of days until your baby seems used to the new flavors. Then you can switch over fully.

More sensitive babies, though, may need a more prolonged approach. In that case, start with three parts of your old formula and only one part of your new formula, then switch to 50/50, and finally to one part old, three parts new before using the new formula exclusively. If you have enough of the old formula, you can give your baby a few days on each one of these steps to adjust more slowly.

Advertisement | page continues below

Remember, though, that this isn't necessary unless your baby is struggling with the adjustment.

Watch a pediatrician demonstrate how to make baby formula and store it safely.

Side effects of changing formula

You may be worried that switching formulas will cause side effects, especially tummy-related ones, but the good news is that side effects are uncommon (and any that do pop up should be pretty temporary, resolving within a few days). The most common side effects of switching formula are fussiness after feedings and changing stool patterns, either looser or less frequent.

It's not a sign of trouble if your baby's poop changes in frequency or color. Remember that formula makes up a big part, if not all, of your baby's diet when they're young. If you changed your entire diet overnight, your bowel movements would probably change, too! Your baby's stomach may need some time to adjust to new or different ingredients.

Some parents worry that excessive gas or other bowel oddities indicate a difficulty tolerating a specific kind of formula. But the truth is that all babies have gas – a lot of gas – so gas alone doesn't mean your baby can't handle whatever kind of formula you're giving them.

It also doesn't mean they have an allergy to cow's milk. (Incidentally, many children who are allergic to cow's milk-based formulas are also allergic to soy-based formulas, so if you think your baby is allergic to milk, switching to soy isn't recommended.)

Advertisement | page continues below

If your baby's stool suddenly becomes very firm after starting a new formula, they may be constipated. This isn't an immediate cause for alarm, and can happen when switching formulas, since your baby's stomach is sensitive to changes.

Try these basic remedies for easing constipation at home:

  • Give your baby a warm bath.
  • Move their legs in a "bicycle" pattern.
  • Give them a small amount of 100-percent prune juice once a day. While babies aren't supposed to have juice before they're a year old, a little bit is okay and might help relieve their constipation. If your baby is younger than 4 months old, talk to your pediatrician before trying this.
  • If your baby has started eating solid food, give them pureed pears or prunes, or whole-grain cereal like cooked oatmeal.

If your baby still doesn't poop after trying these tips, if they've gone five or more days without a bowel movement, or if trying to pass stool seems to cause them pain, call your baby's pediatrician. They may advise you to use a suppository or another medication, but only do this at their recommendation.

Of course, there is always a chance that your baby won't tolerate their new formula well. Don't ignore side effects like rashes, itchy or irritated skin, frequent diarrhea, fatigue or lethargy, and vomiting. If there's blood in your baby's stool or in their vomit, call your baby's doctor immediately. These are signs of a true formula intolerance.

Advertisement | page continues below
Follow your baby's amazing development

BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

American Academy of Family Physicians. 2020. Infant Formula. a new window [Accessed June 2022]

American Academy of Pediatrics. 2022. Choosing an Infant Formula. a new window [Accessed June 2022]

American Academy of Pediatrics. 2022. What should I know about the infant formula recall? a new window [Accessed June 2022]

Nationwide Children's. 2022. Constipation: Infant. a new window [Accessed June 2022]

Nemours Foundation. 2018. Milk Allergy in Infants. a new window [Accessed June 2022]

Mayo Clinic. 2022. Infant formula: Your questions answered. a new window [Accessed June 2022]

Minnesota Department of Health. Undated. Changing Formulas. a new window [Accessed June 2022]

Seattle Children’s. 2022. Constipation. a new window [Accessed June 2022]

U.S. Centers for Disease Control and Prevention. 2022. Infant Formula Preparation and Storage. a new window [Accessed June 2022]

Sarah Bradley

Sarah Bradley is a freelance health and parenting writer from Connecticut, where she lives with a lot of boys (a husband, three sons, and a golden retriever). When she isn't writing, Bradley is usually homeschooling, binge-watching TV shows, and taking care of her many houseplants. She might also be baking a cake.