How to Change Baby Formulas- A Practical Guide for Parents

Whether you're considering a new brand, moving to the next stage, or dealing with a stock shortage, switching infant formulas is something many parents face. The good news? For most healthy babies, it’s safe and manageable—with the right approach, it can be a smooth transition.

Do you need to switch formula's?

Switching formulas is generally safe for healthy babies and doesn’t affect their nutrition. However, it's not always needed. Because babies have sensitive tummies, frequent changes can lead to more discomfort than benefit.

Before switching, ask yourself: Is there a good reason to make this change?
Unless there’s a significant issue, it’s usually best to stay on the same formula for a few weeks to give your baby time to adjust.

When to Consider Changing Formula

If you’re unsure, about your babies health it's always best to speak with a healthcare professional—especially if your baby has health concerns or was born prematurely.

Here are some common reasons to consider switching:

• Allergies or intolerances: Suspected or confirmed reactions to cow’s milk protein or other ingredients. 

• Digestive sensitivities: Like persistent reflux, constipation or temporary lactose intolerance.

• Availability or cost: Stock shortages or needing a formula that’s easier to find or more affordable.

• Moving to stage 2: While not essential, some brands suggest switching to Stage 2 Follow-on Formula from 6 months. Read our article here on follow-on formula. 

• Medical advice: A healthcare provider may recommend a specialty formula for certain health needs.

How to Transition Formulas: Step-by-Step

1. Know Your Reason

Understanding why you're switching helps guide your choice and method of transition.

2. Check the Label

Compare ingredients carefully—differences in formula composition can affect digestion and acceptance.

Key things to look for:

• Protein source: cow’s milk, A2, goat, soy, hydrolysed, rice, pea or amino acids

• Carbohydrates: lactose, maltodextrin, starch, glucose syrup

• Optional additions: prebiotics (GOS, FOS, HMOs), probiotics, thickeners

• Allergen warnings: usually listed beneath the ingredients

Taste and ingredients can impact how your baby accepts and adjusts to the new formula. 

3. Choose Your Transition Method

Straight Swap

This method is safe for most babies—just monitor for any reactions over the following days.

Recommended if you're changing due to:

• Allergies or intolerances

• Medical advice

Gentle Transition 

It gives your baby time to get use to the taste and helps their tummy slowly get use to any change in ingredients. 

There are two gentle transition methods:

• Swap one feed at a time: Replace one feed with the new formula every day or two.

• Mix old and new formula in the same bottle: This method is generally not recommended and is a bit more complex but some parents use it to help with taste acceptance. 

One Feed at a Time Method

Transition to the new formula with morning feeds first. 

Every 1-2 days, gradually replace one more feed to the new formula. 

What to look for during a formula transition?

Sometimes babies adjust to a new formula with no noticeable changes. But often, you might observe some differences—most of which are mild and temporary.

Changes in feeding behaviour

Your baby might:

• Taste the new formula and lose interest (e.g. pulling away from the teat, turning their head, closing their eyes, firmly closing their lips, or pushing the bottle away)

• Drink less than usual

• Show more interest in solid foods, especially if they’re not finishing bottles

Digestive changes

It’s common for babies to experience mild digestive changes as they get used to a new formula. These usually settle within 1–2 weeks and may include changes in:

• Stool colour, consistency, or frequency

• Gassiness

• Fussiness

• Spitting up 

These symptoms aren’t usually a cause for concern. Just go at a pace that suits your baby and give them time to adjust.

Seek medical advice if you notice:

• Persistent vomiting

• Diarrhoea, blood or mucus in the stool

• A widespread rash or hives

• Signs of an allergic reaction (e.g. swelling, wheezing, difficulty breathing)

• Ongoing refusal to feed 

Formula Change Tracker 

To help you track your changing formulas we have put together a simple tracker. Just join MyTots™ Essential membership for free to get access to it in our resources for one month, here.