Combi feeding: how to combine breastmilk and formula

A common question from new parents when it comes to feeding their baby is ‘should I combine formula and breastmilk?’

The answer is that how you feed your baby is completely up to you. Some mums exclusively breastfeed, some stick to formula feeding, and others choose combination feeding (also known as combi feeding or mixed feeding).

Combination feeding is exactly what it sounds like – combining breastfeeding and bottle feeding, either with expressed breast milk or formula¹.

Some parents find that combi feeding works really well for them and their schedule, but that doesn’t necessarily mean it’s the right choice for you.

Here we’ll get into all the details of combi feeding so you can make an informed decision about your baby’s feeding journey.

You might be thinking about combination feeding if¹:

• Your baby was bottle-fed when they were born, and you’d like to start breastfeeding
• You’re experiencing some breastfeeding challenges (like low milk supply, for example), and you want to top up breastfeeds with formula
• You’re looking for ways for your partner or family to get involved in your baby’s feeding routine
• You’re going to be away from your baby for longer periods (e.g. because you’re going back to work)

At the end of the day, it’s all about finding a feeding routine that works for you and your baby so that they get all the nutrients they need for a great start – whatever that looks like.

It’s normal to hit some road bumps when you’re changing your feeding routine, and that includes switching to combi feeding.

Here are some of the most common challenges you might experience when you’re combining breast and bottle.

Your milk supply works on a clever system of supply and demand – the more you breastfeed, the more milk you produce. If you replace some breastfeeds with formula, your body is likely to start producing less milk³.

That’s why it’s recommended that you try exclusively breastfeeding at first to establish a good milk supply before adding formula into your routine³. 

If your body is making more breast milk than you’re using, it can sometimes build up and lead to a blocked milk duct. The duct can then become inflamed and cause flu-like symptoms, which is known as mastitis³.

To try to avoid blocked milk ducts, switch to combination feeding gradually to help your body’s supply and demand system of milk production keep up⁴.

Can you mix breast milk and formula? Absolutely. Here are our tips for starting combi feeding to set you up for success.

Technically, you can start combi feeding as early as you like. But the general advice is to try to reach a point where you and your baby are comfortable with exclusively breastfeeding before you introduce a bottle to help stimulate your milk production⁵.

Before you start combination feeding your baby, have a think about some of the things you’ll need.

Make sure you have⁶:

• Feeding bottles with caps and teats
• Sterilising equipment and brushes
• A breast pump if you’re planning to bottle feed with expressed breast milk

If you’re combination feeding with formula milk, you’ll need powder or ready-to-feed liquid formula. For formula feeds before your baby reaches twelve months old , make sure you buy first infant formula unless your healthcare provider has advised otherwise⁷.

Introducing combi feeding can be a big change. While some babies adapt quickly, others might take a little longer to get the hang of their new feeding routine – especially if they’ve been exclusively breastfed for a while⁸. Remember to give yourself and your little one the time you need to adjust.

There are some things you can try to help set you up for success, like¹:

• Using a slow-flow bottle teat – these can make the milk flow in a similar way to breastfeeding
• Giving your baby the first few bottles when they’re feeling happy, relaxed and not too hungry
• Letting other people handle the first few bottle feeds – if you’re physically close to your baby, they might smell your breast milk and be less likely to take a bottle

You can read more about switching between breast and bottle feeding here.

Not all combi feeding means introducing a bottle to a breastfed baby – sometimes it can be the other way around!

If your little one has been exclusively bottlefed and you’d like to start increasing breastfeeds, try these tips⁴:

• Get lots of skin-to-skin time with your baby to help increase your milk supply.
• Express your milk regularly (ideally about 8 times per day) to boost hormones that increase your milk production.
• Let your baby breastfeed little and often to help them practise latching on.
• Time breastfeeds when your baby is happy, alert and not too hungry.
• Over time, gradually increase breastfeeds and reduce the number of bottle feeds.

‘Nipple confusion’ is a term used when a baby seems fussier about breastfeeding after they’ve been introduced to a bottle. There isn’t much evidence around nipple confusion – it might be that your baby is just getting used to the different sucking patterns needed for breastfeeding and bottle feeding⁹. 

It’s unlikely that combination feeding will increase your baby’s chances of developing colic. Around 1 in 5 babies experience colic regardless of whether they’re breastfed, formula-fed, or a mix of both¹⁰.

To help with milk production while combination feeding, try to express about 7 times a day and once at night. You might find it easier to express by hand at first before using a breast pump if that’s something you’d like to do⁴.

No, while your baby is on a milk-only diet (whether that’s breastmilk or formula), they don’t need water. Once you start feeding your little one solid foods when they’re around 6 months old, you can start offering them small sips of water with meals⁷.