Supplementing Breast Milk with Formula

Many parents need to supplement breast milk with formula. But trying to figure out the best way to do it can be confusing – should you mix breast mix and formula together? Or give breast milk first, and formula only as needed? Here are different ways to supplement with formula, plus some other tips for success.

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For the first month after my son was born, he wasn’t gaining enough weight, and I needed to supplement. I was also constantly pumping and trying to figure out when I should give him breast milk and when I should give him formula.

For example, I’d read somewhere online that I could mix it together in one bottle. I’d also read that giving formula might help my baby sleep longer at night. Or maybe I should just use all of the breast milk I had until I ran out, and then give him formula?

3 Ways to Supplement with Breast Milk with Formula

Here are the different ways you can manage supplementing with formula when you’re exclusively pumping.

1. Mix breast milk and formula together in one bottle

With this method, you prepare formula and breast milk separately, and then combine them in the same bottle.

PRO: If your baby is accustomed to breast milk, he is more likely to accept the bottle, as the flavor will be more like what he’s used to. Also, you only have to make one bottle.

CON: If your baby doesn’t finish the bottle, it will have to be thrown out an hour after he starts drinking it. (Breast milk-only bottles can be kept for two hours after the end of a feeding, while formula bottles must be discarded an hour after the feeding begins.) Throwing away breast milk – especially when you are supplementing – is painful!

2. Start baby with a breast milk bottle and follow with a formula “chaser”

With this option, you give your baby all of the milk that you have available for the feeding, and then offer him formula after the breast milk bottle if he is still hungry.

PRO: No throwing away breast milk! Also – if it is important to you to minimize formula, with this option, you are only giving your baby the amount of formula that you have to.

CON: You have to prepare and wash two bottles. Also, if your baby doesn’t like the taste of formula, he might refuse the second bottle and still be slightly hungry and cranky.

3. Pick one or several feeds of the day to be formula feeds and only offer formula at that feeding

Here, you’d decide how many feedings need to be formula based on the amount of breast milk that you have, and then designate each feeding to be either breast milk or formula, but not both.

PRO: It’s much simpler – only one bottle to deal with and one liquid to prepare. And again, no throwing away breast milk.

CON: If your baby doesn’t like the taste of formula, it might be difficult to get him to take this feeding. However, it’s more likely that he’ll take it since he’ll likely be pretty hungry (versus option #2, where he’ll already have partially filled up on breast milk).

I asked on instagram which one people preferred, and most said that they did the third option, where they had designated breast milk feedings and designated formula feedings.

Rules for Mixing with Breast Milk and Formula in the Same Bottle

If you decide to go with option #1, where you put everything in the same bottle, here are some guidelines and best practices.

Mix formula before adding to breast milk

If you’re using formula that needs to be prepared, mix and prepare it according to the instructions first, before adding it to your breast milk.

Do not add the powdered formula directly to your breast milk unless you doctor directs you to do this. (This doesn’t apply if you’re using ready-to-feed liquid formula; only powdered formula.)

Follow the rules for both breast milk and formula

When feeding from a mixed bottle, need to follow feeding and storage guidelines for both milks. You should discard milk based on the earliest time that would apply to any milk in the bottle.

Other tips for supplementing with formula

Below are a few additional tips for other parents who have done it:

• Pick feeding(s) where your baby is less likely to finish a bottle to be formula feedings, so that you don’t waste breast milk.
• Along the same lines, many parents decide to formula feed at times when warming up a breast milk bottle is inconvenient (often in the middle of the night, or on the go).
• Some parents make a pitcher of formula in the mornings, and then add from this pitcher to breast milk bottles as needed.
• If you just need supplement a small amount of formula, using pre-made formula may be easier than powdered.

Let me know if you have any questions on supplementing with formula in the comments!

Confused about all the rules for handling breast milk in different situations? Worried you’re throwing away milk that you don’t have to? Not sure how to travel with your milk or feed baby on the go? Check out the Ultimate Breast Milk Storage Workshop here! Use MILK10 for 10% off.

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