Choosing to combo feed your baby, which involves toggling back and forth between the breast or pump and bottle, is an excellent option for many families. Moms may decide to both breast- and bottle-feed to combat a low milk supply, when breastfeeding twins (or more!), when heading back to work, to grab more sleep at night or simply because it works best for their schedule.
Depending on your family’s routine, there may be times when it would be convenient to mix the two liquids in the same bottle (for example, if you don’t want to prepare two separate bottles for one feeding, or if you're in the process of transitioning to formula and want to help your exclusively breastfed baby adapt to the new taste).
Read on for the pros and cons of mixing formula and breast milk, how to do it and important safety tips to keep in mind.
Can you mix breast milk and formula in the same bottle?
The good news? If you follow safe preparation guidelines, it’s fine to offer up breast milk and formula in the same bottle.[1]
Pros
When you’re nursing exclusively, the job’s all yours. But combination feeding lets you stretch your breast milk with formula and let other caregivers pitch in with feedings.
Combining breast milk and formula can be a great help to a mom heading back to work, one with a low supply or one trying to nurse multiples. And mixing breast milk and formula in one bottle can be the most convenient way to combo feed, since you’ll wash fewer bottles.
Cons
One drawback to consider, though, is the potential waste involved. Pumping can be a lot of work, and when you mix breast milk with formula together, it shortens the life of the bottle.
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Fresh breast milk lasts up to four hours at room temperature, but with formula added in, the mixture is only good for two hours[2]. And once your baby starts drinking from a bottle, it needs to be tossed after one hour. So, if your little one doesn’t finish the half-breast milk, half-formula bottle in one feeding, you may end up throwing out some of your hard-won breast milk.
The fix here is to offer breast milk first and then, if your baby is still hungry, prepare a few ounces of formula to serve up afterwards.[3]
How to mix breast milk and formula together
For each formula type you’re serving, it’s critical that you follow the manufacturer's instructions to the letter when preparing it before adding breast milk. Here’s how:[4]
Mixing concentrated liquid or powdered formula with breast milk
- Wash your hands, clean your kitchen counter and make sure all gear (the bottle, nipple, measuring scoop, can top) is clean.
- Read the directions carefully and prepare the formula according to the manufacturer’s instructions.
- Once the bottle is made, you can add in any breast milk you’ve expressed.
Mixing ready-to-feed formula with breast milk
- Wash your hands, clean your kitchen counter and make sure all gear (the bottle, nipple, measuring scoop, can top) is clean.
- Because ready-to-serve formula is already prepared, you can simply pour it into the same bottle as your expressed breast milk.
Safety guidelines when mixing breast milk and formula in the same bottle
When you’re making a combination bottle, never be tempted to use your breast milk as a substitute for water when mixing powdered or concentrated formula. It might seem like a way to “pump up” the calories or nutritional content of a baby’s bottle, but this isn’t the correct recipe and a bottle made this way can be dangerous for your child.[5]
A bottle that’s mixed with the wrong amount of water (or with expressed milk and no water at all) can throw off the careful balance of vitamins, minerals, electrolytes and other vital nutrients in the formula. Always follow the guidelines on the packaging and prepare the formula in a separate bottle as directed first, then add any expressed milk you want to use.
When you’re mixing breast milk and formula, keep in mind that this mix is good at room temperature if freshly made (that is, your baby hasn’t sipped from it) for two hours, whether it has breast milk in it or not. But if your baby has taken part of the bottle, it must be used within one hour of starting.
Prepared formula made from concentrate or powder should be stored in the fridge and served within 24 hours, whether it contains breast milk or it’s an all-formula bottle.
Remember that any amount of breast milk is beneficial for your baby, and combining formula with your milk in the same bottle can be safe and convenient. Just be sure you’re mixing it correctly so your baby gets the best (and safest) nutrition every time.
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