Feeding Your Baby

Switching baby formula— Everything you need to know about how to switch from one baby formula to another


Formula changes happen for many reasons. There are allergies and medical issues as well as formula shortages and recalls. Babies can often switch formulas with no problems— even if that has to happen immediately due to unforeseen circumstances. You may be wondering if switching formula can be done quickly or how long it takes for a baby to adjust to a formula change?

We spoke to Dr Lauren Crosby, board certified pediatrician, AAP Spokesperson and Bobbie Medical Advisor, to get all the answers when it comes to making a formula switch. She shares her steps in making the change and assures us that YES— a formula switch can happen cold turkey.

What is the latest news in the world of baby formula and recalls?

Dr Crosby: On February 17, 2022, the FDA announced a warning that prompted a voluntary baby formula recall of certain lots of powdered formula— Abbott Nutrition’s Similac, Alimentum and Elecare. No other formulas have been recalled. This alert was prompted by reports of 4 children who were hospitalized in 3 states due to infections from Cronobacter sakazaii and Salmonella Newport. In these cases, infections are extremely rare and not a reason to panic. Fortunately, there are many options for infant formula to replace those that have been recalled.

How do I know if I was affected by the recent baby formula recall?

Dr Crosby: If you have the brands mentioned, to identify these cans look for a code printed on the can near the expiration date. The recalled cans must meet three criteria:

The first two digits of the code are 22 through 37.

The code on the container contains K8, SH or Z2.

The expiration date is 4-1-2022 (APR 2022) or later.

Can you switch baby formula cold turkey?

Dr Crosby: In a situation like what is happening now with recalls, parents may need to pivot to a different formula quickly— and that is perfectly fine to do. You can just throw out the recalled formula and start with an equivalent formula ASAP.

According to the Switch Study— a recent clinical study by University of Virginia researchers, switching baby formula brands is safe and well tolerated in infants. In this specific study, funded by Perrigo Nutritionals, babies who switched from one milk-based formula to another milk-based formula didn’t experience an increase in spit up, burping, gas, crying or irritability compared to babies who stayed on the original milk-based brand.

“Based on data in our study, there is no statistically significant difference in tolerance variables in changing a baby’s formula,” says James L. Sutphen, M.D., Ph.D., of the University of Virginia department of pediatrics and the study’s lead researcher. “Switching baby formula brands is well tolerated, and we discovered there is no advantage to gradually switching versus immediately from one formula to another.”

How to make the switch from one baby formula to another?

Dr Crosby: If your child is on a cow milk-based formula, you can just switch over to another cow milk-based formula. If your child is on a special hydrolyzed/ hypoallergenic formula, you want to switch to the same type of hypoallergenic formula. Some are more hypoallergenic than others so if you are not sure what is equivalent, definitely check with your child’s doctor.

How do I change baby formulas gradually?

Dr Crosby: If you are making a transition and have some of the old brand left that is not on the recall list, you could start by mixing 3 parts old formula and one part new formula. If the baby drinks it, move to half and half and then 1/4 old and 3/4 new. Following that would be a full bottle of the new brand.

If you need to switch immediately for health or recall concerns, don’t take the time to transition.

How long does it take baby to adjust to a new formula?

Dr Crosby: Sometimes when changing formulas, babies notice a difference in the taste, and this is more common with older babies. Often they get used to a new one quickly, but if they are giving you a hard time you should wait until they are very hungry as then they may be more accepting of a change. 

What are the side effects of switching formula?

Dr Crosby: Typically if you’re switching to the same type of formula there shouldn’t be any significant side effects. Some babies are more sensitive to change than others. They might dislike the taste or they might spit up more.

Poop consistency might change. Babies might get constipated, or poop more often, or have more runny poops, or be gassy or more fussy. It can take a week or so for a baby to adjust to the change but if the symptoms are overall not causing much distress, it is ok to give it some time. If you have any concerns about side effects of changing formula reach out to your baby’s pediatrician and they well let you know what is normal.

How long does it take to change your baby’s formula?

Dr Crosby: One to two weeks is a good transition period depending on how the baby is doing and how quickly the parents feel comfortable making the change. 

How long after changing baby formula do you see side effects?

Dr Crosby: Usually a week is enough time for the baby to have fully transitioned to the new formula. You can monitor the baby’s symptoms that were the reasons a change was made. Some babies take to a change easily and some babies’ tummy’s need to adjust. It’s a good idea to monitor the volume of formula intake, poop consistency, sleep schedule, spitting up, skin changes and look for blood in the stool. If you see any thing concern give your pediatrician a call.

How can I tell if a formula isn’t working for my baby?

Dr Crosby: These symptoms could mean that your formula is not agreeing with your baby. Speak to your pediatrician if you recognize any of the below signs.

Spitting up more than usual

Not drinking enough volume

Hard poops

Watery poops

Blood in the poop

Crying more/more fussy

Not sleeping well

Skin rashes

Top reasons to change baby formulas:

Switching from cow’s milk to another type of infant formula

Switching between liquid, powder or Ready to Feed

Parent’s preference on brand and/or ingredients

Switching from non-organic to organic formula

Formula shortages and/or availability

Formula recalls

Signs and symptoms of an allergy, like a cow’s milk allergy:

Dr Crosby: If parents suspect an allergy, they should see their baby’s doctor to discuss their concerns, and have the baby weighed and examined. It’s a good idea to bring a fresh poop sample to the doctor visit. Allergy symptoms may include:

Spitting up more than typical

Poor appetite

Not gaining weight well

Watery poops

Blood in the poop

Crying more/more fussy

Not sleeping well

Skin rashes 

When to switch to sensitive baby formula?

Dr Crosby: If your baby is very fussy, spits up constantly, is not gaining weight or feeding well, has blood in their stool, is very gassy or sleeps poorly because she seems to be uncomfortable, it’s time to talk to your pediatrician and see if it’s time to change to a sensitive infant formula.

There are different types of sensitive formulas depending on the baby’s symptoms.  Some are truly hypoallergenic— meaning the proteins are broken down so they can be digested more easily. These are for babies with cow milk protein allergy. Other formulas contain partially hydrolyzed proteins which can work for babies who have tummy symptoms like gas and/or fussiness and/or spit up and/or constipation but not a true milk allergy, and the symptoms are not as severe. Some formulas are  made for “lactose sensitivity” but babies in general don’t have lactose intolerance so typically if that formula helps, it is because it also has some of the proteins broken down for easier digestion.

When to switch formula because of gas?

Dr Crosby: Often parents think gas is the reason their baby is fussy, but that is not always the case. It can be one reason why a baby is fussy.

If a baby cries a lot, then passes gas and seems relieved, then gas is likely the issue. If these episodes are not causing the baby to be very upset for a lot of the day, then it is fine not to do anything as long as the baby is growing well, pooping well without any blood in the stool, is happy and sleeping pretty well. If you think the baby is gassy, then make  sure the baby burps well and consider trying a different type of bottle/nipple.  An over-the-counter gas remedy might be recommended by your pediatrician as a next step, and if that doesn’t help then she might recommend a formula switch.

Does a formula switch between milk and soy need to be immediate?

Dr Crosby: Hardly anyone uses soy formula anymore because up to half of babies allergic to cow milk protein are sensitive to soy. If the MD says switch, then something is going on with the baby. The urgency depends on how the baby is doing and your pediatrician will guide you through the swap. If there is blood in the stool or the baby is not gaining weight relay this information to your pediatrician and they will let you know if an immediate switch is recommended. 

Summary about switching baby formula

Whether parents are exclusively formula feeding or supplementing with formula, there are lots of reasons a formula switch may happen. There may be a medical problem, a parent preference or a problem getting the usual formula. In general, this is a safe thing to do, but it’s always important to involve your baby’s healthcare provider so you can get the best guidance on how to switch and what formula is best for your baby.

The content on this site is for informational purposes only and not intended to be a substitute for professional medical advice, diagnosis or treatment. Discuss any health or feeding concerns with your infant's pediatrician. Never disregard professional medical advice or delay it based on the content on this page.

The content on this site is for informational purposes only and not intended to be a substitute for professional medical advice, diagnosis or treatment. Discuss any health or feeding concerns with your infant’s pediatrician. Never disregard professional medical advice or delay it based on the content on this page.

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Meet the Author

Jenny Altman

Jenny is the head of content at Milk Drunk and a writer for all of her favorite wellness and mom sites including Well+Good, Peanut, Motherly and Scary Mommy. Mom to Luisa, she can be found talking bras and beauty with the moms at school and @IAmJennyAltman