Combination Feeding 101

It doesn't have to be formula vs. breast milk — you can totally do both.

Originally Published: 
The 2023 New Parents Issue
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All babies need to eat, sleep, and poop (on repeat), but there is nothing one-size-fits-all about that process, especially when it comes to feeding. You can do it directly from a body or a bottle, give them breast milk or formula, or a blend of it all, called combination feeding. We’ve put together a helpful guide on how to combination feed a baby for every situation: for the short or long term, using mostly breast milk or formula, supplementing each milk feed with formula, or replacing entire nursing sessions with formula-filled bottles.

Yes, the American Academy of Pediatrics (AAP) recommends babies exclusively drink breast milk if possible for approximately six months, but that simply does not work for every family. That’s where combination feeding might come into play. And even that may look different from one family to the next. It all counts as nourishment if baby is healthy, happy, hydrated, and growing. “In the end, the most important thing is that your baby is fed and that you are empowered in the choices you are making to do that,” Dr. Rebekah Diamond, M.D., pediatrician and author of Parent Like a Pediatrician, tells Romper.

Read on for everything parents should know about combination feeding, including how to start introducing bottles and formula, when to start combination feeding, and how to lock down the right ratios and know your baby is satiated.

What is combination feeding exactly?

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Combination feeding refers to providing a baby with both infant formula and breast milk, either directly from the chest or from a bottle. That might mean offering both at each feed or supplementing formula for one or more feedings. Introducing formula, which is regulated in the United States, can be helpful or even necessary for a baby to thrive.

Like the AAP, Rachel Levine, an international board-certified lactation consultant (IBCLC) at NYU Langone Health, notes that exclusive breast milk feeding for the first six months is recommended as the optimal form of nutrition for babies, but she adds that “any breast milk is beneficial for baby’s and mother’s health.” That is why parents are advised in the first few days of a baby’s life to feed breast milk or colostrum, the first form of milk from the mammary glands, often referred to as “liquid gold,” and then top off the feeding with formula, if necessary.

Combination feeding allows a baby to get all the additional good stuff that is provided in breast milk, like antibodies to help fight infection in immature immune systems and age-appropriate nutrition. Breast milk actually changes to meet a baby’s needs as he or she grows. “Antibodies are always present in breast milk, so the baby will receive some benefit no matter how much they get,” explains Levine, although adding that “breast milk benefits are ‘dose dependent’ — meaning benefits accrue the more and longer baby receives breast milk.”

[Note: The AAP explains that the term chestfeeding is more inclusive and accurate than breastfeeding when referring to gender-diverse families.]

Why choose combination feeding?

The short answer is that it is simply one’s choice. “Exclusive breastfeeding can be challenging and maintaining a full milk supply can be hard — some parents choose to combine breast milk and formula feeds so they do not have to pump when away from baby,” pediatrician and certified lactation consultant Dr. Elena Shea, M.D., tells Romper. “Some parents choose to combination feed to protect their mental health if they feel that nursing exclusively is causing them anxiety.”

Here are some reasons why parents might find that combination feeding is right for them and their baby:

  • Breast milk supply is low: It may be taking a long time to come in after childbirth or to establish.
  • To help baby gain weight.
  • To protect parents’ mental health (for example, the lactating parent is anxious about their milk supply and being the sole source of food).
  • Other caregivers can help feed and bond with baby when bottle-feeding.
  • For convenience (to avoid pumping and/or if the lactating parent is not physically available to nurse at every feed).
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When to start combination feeding

Combination feeding can really be introduced at any age, right after childbirth or months down the line. But as long as a baby’s individual needs or supply is not the issue and there is enough milk being initially produced by a lactating parent, doctors and lactation consultants recommend establishing a full milk supply before supplementing with formula if providing your baby with as much breast milk as possible is a priority for you.

How to establish your breast milk supply

“If mothers are considering this feeding plan as an option, ideally she will first establish her milk supply by breastfeeding or pumping exclusively for the first four weeks of baby’s life,” recommends Levine, who notes that supply is usually well-established within four to six weeks. “These first weeks of consistent milk removal — eight to 12 times per 24 hours — establishes a full supply.”

How to maintain milk supply while combination feeding

How much breast milk is produced depends on how much milk is removed. “If you remove milk every two hours, your body will then make milk to feed your baby every two hours,” explains Shea. So if the goal is to maintain a full milk supply, then there has to be a nursing or pumping session every time the baby feeds, even if given a bottle of formula.

Levine notes that to maintain a good milk supply while combination feeding, milk removal is still necessary at least seven to eight times every 24 hours. “Everyone has a different threshold for when their milk supply will start to decrease,” Levine explains. “For some people, it is fewer than five milk removals per day and for some it might be fewer than eight milk removals. Most people find that if they are breastfeeding or pumping fewer than five times per 24 hours, their supplies may decrease dramatically.”

What to consider when combination feeding a newborn

Diamond tells Romper that there are many times in which some sort of combination feeding is necessary for both a baby and parents’ postpartum needs. But she also writes in her book that “the newborn period is the most critical time for all of this supply-demand coordination, and really sets the stage for the months ahead.” At-the-breast feeding, she explains, not only helps establish a latch and helps sync your hormones with baby’s cues, but it can be more enjoyable and sustainable than pumping.

Of course, she maintains that introducing a bottle of expressed milk or formula at some point during this seemingly “all-day nursing buffet” does not ruin your chances of maximizing breastfeeding down the line. It really is all about understanding your feeding goals and your and your baby’s needs at any moment in time.

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With just-delivered newborns who are losing weight or experiencing jaundice, which is pretty common, Shea says that supplementing these initial nursing sessions with formula feeds — as opposed to replacing them with bottle feeds — is important for establishing supply. “You can offer baby formula after feeds,” explains Shea. “It is then totally OK to transition to exclusive breast milk when the need for supplementation has ended.”

[Note: Feeding babies premature enough to require time in the NICU is often more complex. Experts note that this might involve either adding fortifier to the mother’s milk, donated milk, and sometimes, if necessary, formula — or a combination of these options.]

How to combination feed

Just like feeding in general, there is no one way to combination feed. The schedule and ratios will depend on your baby’s needs and your feeding priorities. Whether you give a combination of breast milk and formula at each feed or replace entire feedings of breast milk with formula, Levine reminds parents to watch the baby for signs of hunger and satiation, and not to panic if they are not eating the exact same amount at every single feeding. “Breastfed babies eat a different amount of milk at every feeding, just as we sometimes eat a light breakfast for instance and sometimes a huge buffet brunch,” she says.

As with any feeding issues, it is best to consult a pediatrician to rule out any health concerns. A board-certified lactation consultant can help with chestfeeding questions and create and maintain a plan that achieves everyone’s goals.

Giving a combination of milk and formula at each feed:

With this method, Levine recommends feeding baby breast milk (from the breast or bottle) first and then offering formula (in separate bottles). The amount of formula will depend on how much the baby gets at the breast. “By about 4 weeks, we're at that 3- to 5-ounce average per feeding,” explains Levine. “So if baby breastfeeds first and likely gets at least some milk, then parents will need to watch as they feed the supplemental bottle for when the baby is no longer hungry — no longer cueing to feed, sleepy, relaxed, or fully asleep.”

Alternating breast milk and formula feeds:

Supplementing an entire feed is OK as long as baby is well fed, the breasts are comfortable, and the desired supply is kept, says Levine.

A note on breast health when skipping feeds

“It is very important to pay attention to how the breasts are feeling,” Levine warns. “If they are constantly getting clogs, engorgement, and possibly mastitis, there needs to be a change of plan.” You might need to pump at least a little bit to drop your supply gradually.

Introducing baby to a bottle and formula:

Levine offers these tips to help babies adjust to a bottle or the introduction of formula:

  • A paced bottle-feeding technique, called intuitive bottle-feeding, can both help prevent baby from rejecting a bottle or preferring it (if you plan to continue nursing directly from the breast). “Paced bottle feeding mimics the pace and rhythm of breastfeeding,” she explains. It puts baby in control of the feeding speed to prevent overeating, as well as gas and reflux from drinking too quickly. In this method, a bottle is held level (as opposed to angled or upside down), and the baby is at an incline or sitting upright.
  • For those babies who don’t seem to like the formula, she says “adding a small amount to a bottle of breast milk and slowly increasing the amount of formula while decreasing the breast milk can help.”
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Breast milk and formula storage guidelines

Both pediatricians and lactation consultants recommend following the CDC’s guidelines for storing and preparing breast milk and infant formula.

  • Breast milk: Can be stored at room temperature for 4 hours, in the fridge for 4 days, and in a freezer for up to 6 months. (12 months is acceptable, but Shea recommends freezing anything older than 4 months in a dedicated deep freezer.) Unfinished bottles must be used within 2 hours of the initial feeding time.
  • Formula: After mixing or opening a ready-to-feed bottle, formula is good for 2 hours at room temperature or 24 hours in the fridge. It cannot be safely frozen and should be used within 1 hour of starting a feed. This is why Shea does not recommend mixing formula with breast milk, unless it is in a situation to get a baby used to taking formula.

Best bottles for combination feeding

Both pediatricians and lactation consultants are reluctant to recommend specific products because every baby is different, as is every dynamic. Some bottles might connect directly to certain breast pumps (convenient for pumping parents), and babies might have their own preferences.

In general, though, Shea recommends bottles with a long nipple as opposed to those that have a big, round nipple. She explains that while these are “advertised as being more breast-like,” they really aren’t and that traditional long nipples actually mimic the shape of a mother’s nipple when elongated in a baby’s mouth.

Levine agrees, adding that while some babies do fine with a wide-neck bottle, “slow flow bottles with nipples that have a very gradual slope from tip of nipple to base are often the most comfortable for breastfed babies.”

These might include:

Some general combination feeding ratios

The ratio of breast milk to formula is highly dependent on each situation. The important thing is that, when combined, babies are eating the recommended amount of either breast milk or formula or both, as outlined by the AAP. And even that is a range that fluctuates for each baby and changes according to age.

“Most breastfed babies, by about 4 to 6 weeks, are eating between 3 and 5 ounces of milk at each feeding,” explains Levine. “The total volume of milk that babies will eat ranges from 24 to 32 ounces in a 24-hour period once milk supply is well established.” As babies grow (newborns eat eight to 12 times a day), they will be able to consume more milk less often — but still maintain a constant daily amount until that naturally begins to decrease with the introduction of solids.

Knowing exactly how much milk to feed or formula to supplement is kind of trial and error. “It is always best to watch the baby,” Levine says, “not to rely on a strict amount whether the baby wants that much or not.”

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Combination feeding do’s and don’ts

Whether combination is a choice or a necessity, there are some general dos and don’ts provided by the experts that might help you through the feeding journey:


  • Try establishing a full milk supply the first 4-6 weeks by nursing or pumping — if lactation is going well, this is your ultimate goal, and all of your and your baby’s needs are being met.
  • Remember that any amount of colostrum and breast milk is beneficial to a baby, offering antibodies and age-appropriate nutrients.
  • Consult with your pediatrician to make sure your baby is hydrated and growing, which means they are eating enough.


  • Be reluctant to offer formula to supplement if initial milk supply takes a few days to come in. (It doesn’t mean you cannot build a supply and even exclusively offer breast milk after.)
  • Mix breast milk and formula in the same bottle if you can avoid it.
  • Stress over a magic milk-to-formula ratio. “The amount of formula to feed your baby and maintain your own sense of feeding empowerment is the right amount,” Diamond notes.

Exclusive breastfeeding is not always a reality, and that is OK. “We know that being a mother is challenging, and breastfeeding can be so hard, and we acknowledge that all families need to make the best decisions for themselves,” says Shea. Combination and exclusive formula feeding are safe, healthy options for those who need or want it.


Dr. Rebekah Diamond, M.D., a hospital pediatrician in New York City, assistant professor of pediatrics at Columbia University, and author of Parent Like a Pediatrician

Rachel Levine, IBCLC, lactation consultant at NYU Langone Health

Dr. Elena Shea, M.D., FAAP, IBCLC, a private practice pediatrician and certified lactation consultant based in northern Virginia and founder of PedsMomLife

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