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A brief overview of mixing breast milk and formula

Zofishan Umair

Zofishan Umair

Zofishan is a journalist, humour columnist, and a mum who has survived nappy explosions mid-air. She has over a decade of experience writing for print and online publications and is currently working on her first book.
Created on May 01, 2024 · 7 mins read
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You wipe down the last bottle and look over to your one and only customer of the night.

'Long day?' You ask.

The look on his face tells you he just wants ‘one bottle of his usual.’ STIRRED. Not shaken.

You both know neither of you can handle another sleepless night. So you get to work. And pull out and prepare a nice, warm bottle of breast milk and infant formula.

Then you proceed to feed your customer and burp him while he tells you about his day with those lovely, blue eyes!

Can you mix breast milk with formula?

Did I just mix formula and breast milk like some fancy mixologist? Well, yeah!

(Hey, just because you’re nursing doesn’t mean you can’t pretend to make some fake drinks!)

And while the American Academy of Pediatrics and the World Health Organization (WHO) advocate exclusively breastfeeding for the first six months, let’s be real. It’s not possible for some mums. And that’s okay!  

Because this is where infant formula, or powdered infant formula, swoops in—ready to save your sanity and the day! It’s a safe alternative that can be served alone or mixed with human milk, otherwise known as liquid gold.

Many caregivers use both. This is called a combination feed and involves alternating between breast milk for some feeds and formula for others.

Baby breast milk and baby's health

Breast milk is amazing! Not only does it change to match your baby’s needs, but it also helps fight infections and lowers the risk of SIDS (sudden infant death syndrome). Breastfeeding is great for mums too; it helps recovery, fights postpartum depression, and lowers cancer risks.

Unfortunately, exclusive breastfeeding is not always possible and leads to breastfeeding burnout and premature quitting. Research shows that using powdered formula alongside breastfeeding for newborns losing weight reduced hospital readmissions.

Formula provides the nutrients infants need to grow and allows parents to adapt to their own needs. Breastfeeding doesn’t have to be all or nothing!

A combination feed uses both breast milk and powdered formula. How much formula? It varies and your lactation consultant can guide you best.

Why parents might consider combination feeding

Despite efforts to boost milk production, some mums struggle with low supply due to hormonal changes, previous breast surgery, medications, or age-related factors. Others opt to combination feed babies when natural methods fail to address the low milk supply.

In the case of multiples, ‘mo’babies, mo milk‘ right?

Well, no. Parents of multiples often choose this practical solution to ensure all babies receive sufficient nutrition. Then there’s sleep deprivation and exhaustion. Allowing a partner to feed a breastfed baby expressed milk mixed with prepared formula gives the mum time for more sleep.

Introducing ready-to-feed formula before bedtime makes the baby sleep longer, offering the parent a longer stretch of uninterrupted sleep. Some parents find that a combination feed allows for flexibility when they return to work.

Whatever your reason, just be sure to gradually transition to combination feeding and focus on the potential changes in the baby’s feeding patterns, such as reverse cycling.

How to safely mix breast milk and formula

Mixing expressed breast milk and formula is easy. You can use a separate bottle. If using a powder formula, follow the instructions to prepare it, ensuring the correct amount of distilled or safe drinking water is added.

  • Be sure to use this within two hours.
  • Never use breast milk instead of water during formula preparation.
  • Maintain the right water-to-formula ratio.
  • Add breast milk separately to ensure the formula’s nutritional content remains intact.
  • Adding too much water can dilute nutrients, while too little water can strain a baby’s kidneys and digestive tract, leading to dehydration and potential neurological issues.

The following pointers give a rough guide on how to ensure safe storage:

  • Breast milk can be frozen in a food-grade plastic container for up to 6 months and refrigerated for up to 24 hours once thawed.
  • Freshly pumped breast milk can be refrigerated for up to 5 days or stored in an insulated cooler for up to 24 hours.
  • Opened liquid formula containers should be refrigerated and used within 48 hours, while premade formula bottles should be used within 1 day.
  • Room temperature breast milk is safe for up to 5 hours, but mixed formula or breast milk and formula should be discarded after 1 hour of use due to rapid bacterial reproduction.

Mixing in the same bottle: Is it safe?

Mixing breast milk and formula in the same bottle is safe.

Always follow the formula manufacturer’s directions and consult a pediatrician before changing your baby’s diet. Mixing allows you to use your stored milk supply longer, as breast milk can be frozen for up to 12 months according to the CDC.

While mixing breast milk and formula in the same bottle is safe, some recommend giving them separately to avoid wasting breast milk if the baby doesn’t finish. Adding formula to the baby’s diet may reduce breastfeeding or pumping, potentially resulting in a low supply. It could also be unsafe for infants on specific formula types to mix breast milk if the parent’s diet causes issues.

Pros and cons of mixing breast milk with formula

1. Convenience and flexibility
Mixing breast milk and formula in the same bottle offers convenience for parents, particularly during busy schedules or nighttime feedings. It provides flexibility in feeding routines, allowing parents to adjust based on their lifestyle, work commitments, or other factors.

2. Quicker adjustment to taste
Combining breast milk with formula may aid in quicker adjustment to the taste of formula for babies accustomed to breast milk. This can reduce potential feeding aversions and facilitate smoother transitions between breast milk and formula feeding.

3. Longer sleep stretches
Formula takes longer for a baby’s body to digest than breast milk, potentially allowing for longer intervals between feeds. As a result, mixing formula may contribute to improved sleep patterns for both babies and parents.

Potential risks and how to minimise them

1. Wasting breast milk
Mixing breast milk and formula in the same bottle can lead to wastage of breast milk if the baby doesn’t finish the entire bottle. To minimise waste, offer breast milk first and then provide formula separately if the baby is still hungry.

2. Not enough milk
Introducing formula to feeding routines may result in a reduction in breast milk supply over time. To mitigate this risk, parents can gradually supplement with formula while continuing to breastfeed or pump to maintain an adequate supply.

3. Potential health risks
Improper preparation of formula, such as using breast milk instead of water when mixing powdered or concentrated formula, can pose health risks to the baby.

Additionally, breast milk mixed with formula has a shorter shelf life than breast milk alone, requiring it to be discarded within an hour of initial use to prevent bacterial growth and potential health issues.

Transitioning between breast milk and formula

It’s hard to convince your baby to try your new drink so here are some tips to help:

  1. If your baby is accustomed to breastfeeding, they may initially resist the bottle (they know mama’s got it and can just smell that stuff!). To ease this transition, have someone else, like your partner or a family member, offer the bottle to your baby. Their different approach may help the baby accept the bottle more readily.
  2. Babies may start preferring the bottle over the breast if they find bottle feeding quicker or more comfortable. This preference can lead to nipple confusion.
  3. Heads up: Mixed feeding can cause changes in the color, smell, and consistency of your baby’s stool. This is normal and usually not a cause for concern.
  4. Be mindful of your baby’s feeding patterns. If you notice any significant changes, such as refusal to breastfeed or excessive fussiness, consult a healthcare professional for guidance.

Like any mixologist, just be sure to keep track of the amount of breast milk and formula consumed to ensure adequate nutrition. If you encounter challenges or have concerns, seek support from a lactation consultant or healthcare provider for personalized guidance and assistance.






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