How To Combine Breast and Formula Feeding

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When I was in nursing school, I carpooled with one of my fellow nursing students who was a new mom. As we got ready to pull out of the parking lot, she prepared a bottle for her son, whom she was going to pick up on the way. 

I watched in amazement as she effortlessly and quickly pulled out a container with pre-measured formula, then attached that container to a bottle full of water that fit perfectly, poured the​ baby formula in, and mixed it expertly without so much as breaking the flow in our conversation by a second.

"Wow!" I said, pregnant myself and impressed with her clear motherhood skills. "That's so awesome! But I thought you said you were breastfeeding? Do you do both?"

She smiled that smile of experienced moms everywhere at us newbies and nodded. "Yup!" she said. "I can't breastfeed him during the day, so he only gets that at night. It works out great for us."

I was so surprised by her words, because as a new mom, for some reason, I had thought of breastfeeding and formula feeding in opposition against each other, as if you could only do one and not the other, like they were two enemies of war. I mean, after all, isn't that the way the "Mommy Wars" depicts it? Like they are on two opposite ends of the baby feeding spectrum? It had simply never occurred to me that it was possible to combine formula feeding and breastfeeding. 

But in truth, moms like my friend, who are combining motherhood and school and work, often have to create a system that works for them and that might just include mixing bottle feeding with formula and breastfeeding too.


Once I added a few babies to my family, I considered doing a combination of formula feeding and breastfeeding because I suffered some milk duct damage from reoccurring mastitis and was worried I wouldn't be able to produce as much milk as my baby needed. I liked the idea of mixing both options if necessary and was pleasantly surprised to find out that it was an option that no one really mentioned when it comes to feeding your baby.

You don't have to choose just one option for feeding your baby and for some families, combining breast and formula feeding might feel like the best of both worlds. Here's how mixed feeding  or formula supplementation works:

How To Combine Breast and Formula Feeding

One of the coolest parts about breastfeeding is that it works on a supply and demand system. So, in other words, your body literally "learns" how much your baby will need to eat and will produce that much milk for your baby. Of course, it can take time to produce the amount of milk supply your baby needs and different factors, such as genetics, diet, stress, or illness, will affect your supply as well. 

And in some cases, a woman might simply need to supplement her baby because of reasons other than personal preference. But whatever your reason may be, if you're hoping to combine breast and formula feeding, your body will adapt to make milk when you want it to, but here a few tips to help make that happen:

1. Establish breastfeeding first

Even if you know you want to add formula feeding into the picture at a later point, it is best to start off with exclusive breastfeeding first. Not only will this ensure that your baby learns how to effectively breastfeed, but it will establish an adequate milk supply for your baby.

It is much easier to taper down that supply when you're ready to add in formal feeding than try to have your body produce more milk. If you add in formula feeding right away, your body might not make enough milk, your baby may not suckle effectively enough, which will further discourage milk production, and you both may get frustrated very early on. You should plan on exclusively breastfeeding for four-six weeks in order to build up your supply and establish a good breastfeeding routine with your baby. 

2. Drop breast feedings one at a time

Once breastfeeding has effectively been established and you have determined that you would still like to continue with mixed feedings, you can eliminate one breastfeeding at a time and replace it with a formula bottle.

Many mothers might find it convenient to try to replace the nighttime feeding with a bottle, as dad or a partner might be able to feed the baby that way, giving her some much-needed rest. To prevent engorgement, you could hand-express extra milk, but be careful not to stimulate the breasts too much, as that could make you produce more milk. 

3. Be flexible

You might have to experiment with different types of bottles or formulas to help your baby adapt to mixed feedings successfully and your baby might prefer breast over bottle at certain times of the day. For instance. we had more trouble getting my babies to take bottles when they were especially sleepy, since they just wanted the breast, more for comfort, so you may have to try different times of the day too before finding a routine of mixed feeding that will work for all of you.

4. Be prepared for changes in your baby

Because the composition of breast milk and formula is so different, introducing formula to a strictly-breastfed baby may cause some changes in the baby's bowel movements. Breast milk has a much different microbial make-up than formula, so don't be alarmed if your baby's poop suddenly changes color. If your baby seems uncomfortable, is spitting up more, or seems constipated, you might want to speak with your care provider if mixed feeding is right for your baby or about trying a different type of formula.


Guaraldi, F., & Guglielmo, S. (2012). Effect of breast and formula feeding on Gut Microbiota Shaping in Newborns. Front Cell Infectitoius Microbiolgy, 2: 94. 

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