Changing baby formula: Your complete guide

If you’re formula feeding, whether exclusively or in combination with breastfeeding, you’ve probably spent a fair bit of time thinking about which brand and type of formula milk to use. And as you stand on that baby aisle at the supermarket, the choice on the shelf can feel pretty overwhelming!

Settling on which formula you’d like to use is a big decision. Sometimes, just when you think you’ve got it figured out, you might decide to make a change.

That’s why we’re here to help. Here you’ll find expert tips on changing formula milk, from signs it’s time to switch to how to make the transition safely.

Yes, you can change your baby’s formula. There’s nothing to suggest that changing formula milk will cause your baby any harm¹.

It’s always best to speak to your doctor or midwife before you make the switch, to ensure it’s the best thing for your baby.

There are several reasons you might be considering changing the formula milk you use. Let’s take a look.

• Availability. Some types and brands of formula milk might not be as widely available as others. See what’s available at your local supermarket, so you’re covered for that last-minute, late-night dash when you realise you’re low on supplies!
• Cost. Prices vary across different brands and types of formula milk, and it’s OK to switch to a formula that better suits your budget. Depending on your circumstances, you might be entitled to receive vouchers from the Healthy Start scheme. You can talk to your midwife about your eligibility and how to apply.
• Your growing baby. As your baby grows older, you might want to move on from first infant formula milk and try follow-on milk after 6 months or toddler milk from 1 year instead.

If your baby has reflux or tummy troubles, your doctor or midwife might recommend changing formula to an anti-reflux or hypoallergenic formula (you can find out more about the different types of formula below).

Some of the symptoms that might lead to a switch include^2,3:

• Red, itchy skin or eczema
• Diarrhoea
• Vomiting or bringing milk back up
• Excessive wind
• Crying and being unsettled
• Tummy pain
• Wheezing, coughing or shortness of breath

These can be signs of an allergy or intolerance, for example, a cow’s milk allergy.

You should always talk to your doctor about your baby’s symptoms first before changing formula milk or making any other changes to your little one’s diet.

If you’ve spoken to your doctor or midwife and decided that changing baby formula is the right thing for your baby, the next step is to introduce the new formula into their feeding routine.

There are two ways of doing this: a gradual transition or a straight swap. 

Changing formula milk gradually is usually recommended, as it’s gentler on your baby’s tummy.

You could gradually increase the number of feeds of new formula over a few days.

For example, if you usually give 5 formula feeds per day, you could follow a schedule like this⁴:

• Day 1: 4 original formula feeds, 1 new formula feed
• Day 2: 3 original formula feeds, 2 new formula feeds
• Day 3: 2 original formula feeds, 3 new formula feeds
• Day 4: 1 original formula feed, 4 new formula feeds
• Day 5: 0 original formula feeds, 5 new formula feeds

Sometimes, like if your baby is still very young or if they have a severe cow’s milk allergy⁴, your doctor might recommend changing formula milk straight away. In this case, you can start using the new formula milk for every feed immediately, doing a ‘straight swap’ without the gradual transition.

If you’re thinking about changing baby formula, it’s good to know what other options there are. From first infant formula and follow-on milk, to hungry baby and lactose-free, we’re taking a look below.   

If your baby is formula-fed, first infant milk will be the first milk that you give them, and it’s suitable for babies up to one year old. 

Follow-on milk is suitable for your baby from 6 months up to 12 months, once they’ve started eating solid foods (and probably making quite a mess doing it!). 

Follow-on formula milks contain a range of vitamins and minerals that complement your baby’s weaning diet (like additional iron) up until they’re one year old. However, if your baby is happy enough drinking first infant formula milk, you don’t have to switch to follow-on milk. 

Toddler milks are suitable from either one or two years (depending on the stage) but always ask your healthcare professional for advice first.

If your baby seems hungry for more after their feeds but is not ready to wean yet, you might consider hungry baby formula. This contains more of a protein called ‘casein’, which takes longer to digest¹. 

Whilst hungry baby milk is suitable from birth, always speak to your doctor or midwife before giving it to your baby. 

Comfort formula is suitable from birth, designed for the management of colic and constipation. Comfort formula is made with partly broken-down proteins from cows' milk, which your baby may find easier to digest¹. 

If your baby has reflux, you might be looking for ways to reduce those spit-ups and outfit changes. Anti-reflux formula milks are thickened and designed to help your baby’s tiny tummy keep feeds down¹. 

You can buy anti-reflux or comfort formula from the supermarket, but you should only use them if a healthcare professional has advised you to do so. 

If you think your baby has colic, constipation or reflux, always run their symptoms by your doctor or healthcare professional first. That way, you can make sure you’re getting the advice you need.

Although uncommon, some babies have lactose intolerance, which means that they can’t break down lactose – a sugar found naturally in milk and other dairy products⁵. If this is the case, your doctor may advise you to use lactose-free formula milk. 

Lactose-free formula should be used under supervision from your doctor.

If your baby has a cow’s milk allergy, your doctor will likely prescribe a hypoallergenic formula milk made from proteins that have been fully broken down¹. Lactose-free formula isn’t suitable for babies with a milk allergy, because it’s the protein that triggers the immune system to react and not the milk sugar (lactose). Comfort formula isn’t suitable either, because the protein is only partially broken down, so it can still trigger an allergic reaction. 

Hypoallergenic formula should only be used under supervision from your doctor or healthcare professional.

There’s no evidence that changing baby formula does any harm¹, but any change in your baby’s diet can show up in their nappies while their little tummy gets used to the switch. 

Their poos might be slightly different in colour or consistency from normal, or they might poo more or less often for a little while. This is usually nothing to worry about and should settle down again soon.

Every baby is different. When changing formula milk, some babies might adapt straight away, while others might take a little longer. 

Most little ones will adjust to changing baby formula within a few days to a week but always speak with your doctor if your baby shows any symptoms you’re concerned about.

It’s important to talk to your doctor or midwife before you make any big changes to your baby’s diet.