Mixing Breastmilk and Formula – Is It Okay?

Mixing Breastmilk and Formula - Is It Okay?

Some parents choose to mix feed their babies, alternating between breastfeeding and formula feeding due to work commitments or for other reasons.

It would be understandable to ask yourself the question, “can you mix breastmilk and formula together?”

The short answer is yes, but there is more to it. It’s actually recommended to give your baby breastmilk first, then the formula.

There are two reasons why it’s better to feed your baby breastmilk and formula separately.

Mixing Breastmilk and Formula Together In A Bottle

Firstly, when you mix breastmilk and formula into one bottle, you may lose precious, expressed breastmilk if the baby doesn’t finish the bottle.

While breastmilk may be refrigerated for a short time, formula needs to be discarded after the feed to avoid the growth of bacteria.

BellyBelly’s IBCLC, Renee Kam says:

“Many mothers who have to express (e.g. for a premature baby) will understand the immense hard work that goes into pumping milk, and won’t want a drop of it to go to waste!”

Secondly, it’s much more nutritionally beneficial to fill your baby with breastmilk first, before giving formula (if it’s then required). The more nutrients, probiotics, and anti-infective factors your baby receives from breastmilk, the better. When you compare what’s in breastmilk and what’s in formula, you’ll want your baby to have as much of the breastmilk as possible. See an ingredient comparison here.

Also, be aware that it’s possible to think your baby is hungrier when you bottle feed. In BellyBelly’s article, 5 unreliable signs that your baby is getting enough milk, Renee discusses how babies may still happily take a bottle, even if they are full. This is because they love sucking — they find it pleasurable. Sucking for hunger is only one of several reasons why they will keep sucking. Here are baby hunger cues.

Important Formula Safety Tips

Renee offers these important formula safety tips for parents:

  • Breastmilk should never be used as the water component for formula.
  • It’s best to make formula only as it is needed. This is because once powdered formula has been made up, it provides ideal conditions for the growth of harmful bacteria.
  • Always make up formula exactly as the directions on the tin state. Different formulas have different instructions and so it’s not possible to give general instructions on how to make up a bottle of formula. For example, it’s important to use the scoop provided with each tin, as scoop sizes vary.
  • Make sure you add the correct volume of water to the bottle first and then add the powdered formula. If you put the powdered formula in the bottle first, then add the water up to the correct volume, the ratio of formula to water could be too strong and this can put strain on a baby’s kidneys.
  • The World Health Organization guidelines recommend to use water that is at least 70 degrees Celcius to make up powdered formula. To achieve this temperature, the water should not be left for more than 30 minutes after boiling. Before giving it to your baby, cool feeds quickly to feeding temperature by holding under a running tap.
  • Never dilute breastmilk or formula with extra water. The results can be fatal. Breastmilk is perfectly balanced for your baby, and formula made as per the instructions on the tin is exactly as your baby needs to drink it. Read more here.

See our article here about the ingredients in breastmilk and the ingredients in formula.

Last Updated: August 5, 2015


Kelly Winder is the creator of BellyBelly.com.au, a writer, doula (trained in 2005), and a mother of three awesome children. She's passionate about informing and educating fellow thinking parents and parents-to-be, especially about all the things she wishes she knew before she had her firstborn. Kelly is also passionate about travel, tea, travel, and animal rights and welfare. And travel.

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