How to Supplement with Formula When You’re Breastfeeding

If you’re considering supplementing with formula while breastfeeding, you’re not alone! Whether it’s due to low milk supply, returning to work, or simply needing a break, supplementing offers flexibility and convenience for the whole family.

It’s common for parents to have concerns or encounter misconceptions (and judgments) along the way—that’s where we come in. In this article, we’ll explain how to begin supplementing with formula while breastfeeding, tackle those common concerns and misconceptions head-on, and ultimately provide you with a practical guide to make supplementing a successful part of your feeding routine. 

What Does It Mean to Supplement with Formula?

Supplementing with formula is exactly how it sounds—adding formula to your breastfeeding routine, whether you’re nursing or feeding expressed breast milk in bottles. You may also see it called combination or combo feeding.

What Are Some Signs You May Need to Start Supplementing with Formula?

Always talk to your pediatrician if you have any concerns about your baby’s growth or eating habits. Symptoms that merit a call include:

  • Insufficient weight gain. While it’s not unusual for newborns to experience slight weight loss in the days following birth, it shouldn’t exceed 7% of their birth weight. By the time they’re two weeks old, they should be back at their birth weight. If your baby isn’t gaining weight according to their growth charts or is consistently falling below growth percentiles, it could suggest that breast milk alone does not provide enough nutrition.
  • Too few wet diapers. Your baby should produce six wet diapers in 24 hours by the time they’re five days old. If your newborn isn’t making the expected number of wet diapers daily, it could signal that they aren’t getting enough milk.
  • Too short or too long nursing sessions. Newborns typically nurse for 20 to 30 minutes. If your baby is nursing for fewer than 10 minutes or more than 50 minutes each session, it could be a sign they aren’t getting enough milk.
  • Signs of dehydration. Watch for signs of dehydration in your baby, such as dry mouth, sunken fontanelle (soft spot on the baby’s head), or decreased urine output. These symptoms could indicate that your baby isn’t getting enough fluids.
  • Lethargy and fussiness. Your baby should be content most of the time. If they’re lethargic or cranky more often than not, it’s time to call your healthcare provider.

How Will Supplementing with Formula Affect Your Baby?

All things concerning infant feeding provoke a lot of understandable anxiety in new and veteran parents alike (we’ve been there!). While introducing formula doesn’t typically create noticeable reactions in babies, you may notice the following:

  • Refusing the breast. Nursing takes longer and requires more effort than bottle feeding. If you supplement regularly, your baby may develop a preference for the bottle.
  • A difference in stools. Healthy formula-fed baby poop is usually yellow or brown and has a thicker consistency than breastfed poop (like peanut butter). Your baby may poop less frequently—but they’ll be bigger and smellier.
  • Less frequent feedings. Baby formula isn’t digested as quickly as breast milk, so your baby will feel fuller longer.

Reasons Why You Might Supplement with Formula

There’s no universal reason parents choose to supplement breast milk with formula—there are many reasons why combo feeding might be the right choice for your family. These are the most common reasons parents add formula into the mix.

You Have a Low Milk Supply

Some women produce less milk than others (if supply is a concern, always reach out to your pediatrician or an IBCLC for guidance). If your healthcare provider has determined your little one isn’t getting enough milk during breastfeeding sessions, formula can help make up for the difference.

Your Pediatrician Recommended Supplementing

If your little one arrived earlier than expected or is having difficulty gaining weight, your pediatrician might suggest adding infant formula to their feeding routine for an extra boost of calories and nutrition. Likewise, if your baby develops jaundice—a condition marked by elevated bilirubin levels—supplementing breast milk with formula could be recommended. This approach not only helps lower bilirubin levels but also may prevent the need for additional medical intervention.

You’re Going Back to Work or School

You may choose to supplement with formula because you’re getting ready to return to work or school. Balancing breastfeeding and a busy schedule can be challenging, especially when factoring in the time-consuming nature of pumping—and most workplaces don’t have dedicated lactation rooms. Finding time to pump for moms juggling multiple responsibilities can be overwhelming (and sometimes impossible). 

You Want to Supplement Overnight

Sleep is a precious commodity, especially for bleary-eyed parents of newborns. Supplementing with formula overnight allows your partner or other caregiver to give your baby a bottle while you squeak in a few extra ZZZs.

Your Partner Wants to Be More Involved in Feeding 

Feeding your baby is more than just nourishing—it’s one of the earliest and easiest ways to bond with your new bundle of joy. Typically, only one parent is breastfeeding, and one partner may feel a little left out. Supplementing with formula solves that problem and ensures everyone can participate in feedings.

Supplementing Just Works for Your Family

If breastfeeding and supplementing work for your family, guess what? You don’t need a reason or justification for that choice. Only two things matter: Your baby gets the nutrition they need, and your feeding approach works for everyone. 

Choosing Formula for a Breastfed Baby

Choosing the right formula for your baby can feel overwhelming, but remember, your pediatrician is there to offer guidance every step of the way.

All commercially sold formulas in the US are perfectly safe for your baby, thanks to strict Food and Drug Administration (FDA) regulations. Cow’s milk-based iron-fortified formulas are the most common choice and are available in powders, concentrates, or ready-to-serve portions. Most healthy babies without allergies or other intolerances do well with this formula.

How to Start Supplementing Breast Milk with Formula

When possible—and sometimes it’s not—wait until breastfeeding is well established before introducing a supplemental bottle (of breast milk or formula). Delaying a bottle for the first three to four weeks ensures that you have a steady milk supply.

When you’re ready to introduce formula, offer a bottle when your baby is calm but not overly hungry or too fussy (an hour or two after nursing is usually ideal). It’s helpful to mimic breastfeeding and make bottle feeding feel like a similar experience. Try lots of skin-to-skin contact—is there even such a thing as too much snuggling?—and switch sides like you might while nursing. 

We recommend using paced bottle feeding while introducing formula bottles: 

  • Hold your baby upright or semi-upright during bottle feeding, similar to how they would position at the breast.
  • Tilt the bottle horizontally so the milk fills the nipple but does not flow freely, encouraging your baby to suck actively to draw milk from the bottle, similar to breastfeeding.
  • Pause periodically during the feeding to allow your baby to rest and swallow, mimicking the natural breaks during breastfeeding.
  • Pay attention to your baby’s cues and stop feeding when they show signs of fullness, like turning away from the bottle, closing their mouth, or becoming less interested in sucking.
  • Gently burp your baby to help release any air swallowed during the feeding and reduce the risk of discomfort or gas.

If your baby is a breast milk bottle pro, they might have some opinions about the taste of formula (it’s not as sweet). You can mix formula and breast milk in a bottle, gradually increasing the formula ratio until your baby has made the switch. Always prepare your formula in a separate container before adding it to the expressed milk, and never add powdered or concentrated formula to breast milk instead of water.

Safely Prepare Your Formula Bottle

Before preparing the formula, prioritize cleanliness by washing your hands thoroughly and sanitizing all bottles and accessories. If you’re using powdered formula, mix it with a safe water source. Concerned about your tap water? Contact your local health department for guidance, or boil the water and let it cool before use.

As for temperature, the Centers for Disease Control and Prevention (CDC) says that warm water isn’t necessary for mixing infant formula—cool or warm, it’s up to you. But if your little one prefers their milk on the warmer side, you can safely heat their full bottle by submerging it in a warm water bath for a few minutes. Remember to steer clear of the microwave—it can create hot spots that burn your baby’s delicate mouth.

Common Concerns When Combo Feeding

You may encounter some resistance when introducing a formula bottle to your baby—breast milk doesn’t taste like formula milk, and sucking a bottle feels different than nursing. Here’s how to troubleshoot the most common problems when introducing formula to your baby.

Will Bottle Feeding Impact Your Milk Supply?

Introducing bottle feeding to supplement breastfeeding can affect your milk supply—it may signal your body to produce less milk if breastfeeding sessions are reduced or skipped. But with careful planning, consistent breastfeeding, and adequate pumping, it’s possible to maintain milk supply while supplementing with bottles.

Does Bottle Feeding Cause Nipple Confusion?

File this one under (mostly) urban legend—nipple confusion rarely happens, and most babies switch between the breast and bottle with zero problems. But if your baby does have trouble, experiment with different nipples (and bottles) to see if changing the flow level or nipple shape solves the problem. It may require patience and perseverance, but eventually, your baby will take to the bottle like a fish to water.

What If Your Baby Refuses the Formula Bottle?

Your baby may initially refuse the bottle, especially if they’ve been breastfed exclusively. If you’re the nursing parent, try letting your partner introduce the bottle first—your little one won’t snuggle up and expect to breastfeed, and that can help. Make sure you’re giving a bottle when your baby shows very early hunger cues. Waiting until they’re overly hungry or upset is a no-go.

Read more: The Ultimate Guide to Bottle-Feeding Your Baby (publish TBD)

Will Formula Make Your Baby Gassy?

Yes, introducing formula can make your baby gassy. Your baby may swallow more air while bottle feeding, so break for burps and make sure the nipple is always filled with milk.

Breast milk is also more easily digestible than formula, and your baby may be sensitive to some formula ingredients, like lactose or milk proteins. If gas and discomfort continues to be a concern, talk to your pediatrician about the possibility of switching formulas. There are specialty formulas that can help with gassiness, fussiness, and colid.

What If Your Baby Chokes on the Bottle?

If your baby chokes on the bottle, it may be because formula from a bottle flows faster than breast milk, surprising them and causing coughing or spitting up. You may need to switch to a nipple with a slower flow rate. Paced feeding can also help prevent your little one from guzzling formula too quickly.

Is Formula Feeding Expensive?

Formula feeding can be a pricey endeavor—choosing to breastfeed exclusively for the first six months can save your family up to $1500 in your little one’s first year of life. Unfortunately, following optimal breastfeeding guidelines can be challenging, and even impossible, for some families. To stretch your formula budget, you can try:

  • Always use powdered formula—it’s less expensive than concentrates or pre-made formulas.
  • Say yes to samples! Most pediatricians have formula samples at their offices.
  • Buy store-brand formula. All formula on the market is safe for your baby (just make sure it’s iron-fortified).
  • Visit your local WIC office. If your family is eligible, you can receive free breastfeeding help and a monthly allotment for formula.

Finding What’s Right for You

Albee Baby is the oldest family-owned specialty baby shop in the US. We pride ourselves on providing our customers with the best assortment of baby products anywhere, at fair prices, always. We’re committed to being an inclusive resource for parents and hope you feel empowered to find the right baby gear for your family. Still have questions? Feel free to contact our baby gear experts at 877.692.5233 or [email protected].