Supplementing with formula when you're breastfeeding

Supplementing is a safe way to provide your baby with all the nourishment they need from breast milk and formula. If you can, start replacing nursing sessions with supplemental formula very gradually. This will help your baby adjust and prevent problems like engorgement. Watch for signs that your baby's getting enough to eat, and contact their doctor or a lactation consultant for help if you need it.

mother bottle-feeding her baby
Photo credit: Katie Rain for BabyCenter

Is it okay to supplement with formula?

Yes. Any amount of breast milk is beneficial, and it's okay to supplement with formula if that's what's best for you and your baby.

Health experts including the American Academy of Pediatrics recommend feeding babies breast milk exclusively until introducing solid foods around 6 months old. But parents may choose to supplement with formula for a variety of medical or personal reasons, such as a low milk supply or the challenges of pumping at work.

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If you're supplementing because of supply issues, you might plan to go back to exclusively breastfeeding if your milk supply climbs again. Or, maybe you've decided to transition to formula before going back to work.  

How to start supplementing

It's a good idea to start cutting back on breastfeeding sessions and giving formula gradually, if you can. This will help you avoid issues like engorgement, clogged milk ducts, and mastitis.

For example, if you want to go back to work and nurse your baby in the morning and at night but provide formula for daycare, you would ideally start cutting out breastfeeding sessions one at a time, very gradually, until most daytime feedings are exclusively formula feedings.


You could start by dropping one feeding every three to seven days. Try to be patient with the process, which may take weeks depending on how your baby does with formula and how your breasts adapt. As you replace nursing sessions with formula feeding, your milk production will slowly decrease. If you experience engorgement in the meantime, pump enough milk to be more comfortable.

If you're still producing enough milk to make your breasts uncomfortable while at work, you could pump occasionally to relieve any engorgement – but not enough to stimulate more milk production.

If you're supplementing because you're not producing enough breastmilk, be sure to nurse your baby first, completely emptying your breasts, before giving your baby formula. This will provide your baby with the most breast milk possible while cueing your body to produce more milk.

When can I start supplementing with formula?

You can start supplementing at any time. However, doctors and lactation consultants recommend waiting until your baby is at least 3 weeks old (if possible) to start supplementing with formula, so that your milk supply and breastfeeding routine has adequate time to get established.

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That way, an occasional bottle won't be too disruptive for your baby or confusing for your body as it starts producing milk. Also, it's usually easier to get your milk supply up by exclusively breastfeeding at first, rather than nursing and formula feeding from the start. This will also give your baby the most breast milk when they're a newborn.

If your baby has a medical issue, such as inadequate weight gain, your doctor or lactation consultant may recommend supplementing earlier.

Will supplementing with formula affect my milk supply?

Yes, your supply of breast milk depends on your baby's demand, so the less often you nurse or pump, the less milk your breasts will produce.

If you supplement with one or two bottles of formula a week, the effect on your milk supply should be minimal. But if you supplement with formula regularly (for example, for one feeding a day) and don't pump, your milk supply will adjust to the reduced demand.

If you need to supplement for medical reasons but would ideally like to breastfeed exclusively at some point, make sure your doctor or lactation consultant know this so they can help you develop a schedule for pumping that will help maintain your milk supply.

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Keep in mind that you won't be able to use nursing as a method of birth control (the lactational amenorrhea method or LAM) if you're supplementing. For this method to be effective, your baby must be younger than 6 months old and you must breastfeed very often.

What are some signs that my baby needs supplemental formula?

Talk to your baby's doctor if you have any concerns about your baby's weight gain, growth, or eating habits. Here are some symptoms that warrant a call:

  • More than normal weight loss in a newborn. Babies should lose no more than 7 percent of their birth weight in the first few days after birth. By 2 weeks, they should be back up to their birth weight.
  • Fewer than six wet diapers in a 24-hour period once your baby is 5 days old.
  • Fussiness or lethargy most of the time.
  • Very short or very long nursing sessions. If your baby often nurses less than 10 minutes or more than about 50 minutes at a time, it may mean they aren't getting enough milk.

Here are reassuring signs that your baby's getting enough formula or breast milk.

How will supplementing with formula affect my baby?

Supplementing with formula may have little obvious effect on your baby, but you may notice:

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  • Your baby might start refusing the breast if you supplement regularly. A bottle delivers milk faster than a breast, so if your baby's an enthusiastic eater, they might prefer a bottle.
  • Your baby might go longer between feedings. That's because babies don't digest formula as quickly as they digest breast milk, so they're likely to feel full longer.
  • Your baby's stool will be different. It will be firmer (about the consistency of peanut butter), be tan or brown in color, and have a stronger odor. Your baby will probably have less frequent bowel movements.

What's the best way to introduce a bottle?

If your baby has never taken a bottle before, they may need a bit of coaxing. Here are some tips:

  • Mimic breastfeeding by cuddling and providing plenty of skin-to-skin contact. Switch sides, as you would if your baby were breastfeeding.
  • Used paced bottle feeding, which is more like breastfeeding: keep the bottle horizontal, use a slow-flow nipple, and pause often during feedings.
  • Let someone else give it a go. If your baby refuses the bottle from you, they may be more receptive to taking it from someone else. Some moms find they even need to leave the house – so their baby doesn't smell them – for their baby to take a bottle instead of breastfeeding.
  • Give your baby the bottle when they're just hungry but not overly hungry and upset. Try to choose a time of day when they're usually in a good mood.

Read more about how to introduce your breastfed baby to a bottle.

If your baby is used to taking a bottle of breast milk, they won't mind the bottle. But they may not like the taste of formula initially. Be patient while your baby gets used to the new taste, and keep trying.

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What's a supplemental nursing system and how does it work?

A supplemental nursing system (SNS) or supplemental feeding system is a way for you to nurse your baby and give them formula (or expressed breast milk) at the same time. The supplemental formula or milk travels along thin, flexible tubes that are taped (with paper tape) along your breasts to the ends of your nipples. When your baby sucks, they receive the supplemental liquid, along with any breast milk you produce.

The system allows your baby to continue to suck at your breast, avoiding any preference for a bottle, while also stimulating your milk production. An SNS is often used if a mother has a low milk supply, but it can also be used by partners and by adoptive parents.

Talk with your doctor or a lactation consultant if this is something you'd like to try.

Learn more:

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Karen Miles
Karen Miles is a writer and an expert on pregnancy and parenting who has contributed to BabyCenter for more than 20 years. She's passionate about bringing up-to-date, useful information to parents so they can make good decisions for their families. Her favorite gig of all is being "Mama Karen" to four grown children and "Nana" to nine grandkids.