Yes, you can absolutely breastfeed and formula feed your newborn. This approach, often called combination feeding or mixed feeding, is common and works well for many families. The key is understanding how introducing formula affects your milk supply and knowing a few practical techniques to keep both methods running smoothly.
Why Parents Choose Combination Feeding
Parents supplement with formula for all sorts of reasons: a perception that they’re not producing enough milk, a short maternity leave that makes exclusive breastfeeding impractical, pain or discomfort while nursing, or simply wanting another caregiver to share feeding duties. None of these reasons require you to stop breastfeeding entirely. Mixing the two is a legitimate feeding strategy, not a compromise.
That said, combination-fed babies aren’t just “a little of both.” Research shows they develop distinct gut bacteria and immune profiles compared to exclusively breastfed or exclusively formula-fed infants. Your baby still gets meaningful immune benefits from whatever breast milk they receive, even if it’s not every feed.
How Formula Affects Your Milk Supply
Breast milk production runs on a supply-and-demand system. Every time milk is removed from the breast (by nursing or pumping), your body gets the signal to make more. When milk sits in the breast, a protein called feedback inhibitor of lactation builds up and tells your body to slow production. This happens on a breast-by-breast basis, so a full breast actively downregulates its own output.
This means every formula bottle that replaces a breastfeed is a missed demand signal. Over days, your supply adjusts downward to match the reduced demand. If you want to keep your supply steady while offering formula, you need to compensate for those skipped sessions, either by nursing at other times or by pumping.
How Many Times You Need to Nurse or Pump
Your “magic number” of breast stimulations per day depends on your current production. The total counts both nursing sessions and pumping sessions together:
- Producing 10+ oz per day: 3 to 4 sessions
- 5 to 9 oz: 5 sessions
- 3 to 5 oz: 6 sessions
- 2 to 3 oz: 7 sessions
- 1 to 2 oz: 8 sessions
So if you’re producing a healthy amount and want to maintain it, you may only need three or four nursing or pumping sessions in 24 hours, with formula covering the rest. If your supply is lower, you’ll need more frequent stimulation to hold steady. In the early weeks, when supply is still being established, it’s generally better to breastfeed frequently and introduce formula gradually rather than dropping multiple feeds at once.
Two Ways to Structure Mixed Feeds
There are two main approaches, and you can use either or both depending on your day.
Alternating feeds means some feeds are entirely breast milk and others are entirely formula. For example, you breastfeed in the morning and evening but your partner gives a formula bottle during the afternoon and overnight. This is the simpler method and works well once your supply is established, typically after the first three to four weeks.
Top-up feeds means breastfeeding first and then offering a small amount of formula afterward if your baby still seems hungry. This keeps breast stimulation high because you’re nursing at every feed, with formula just filling the gap. It’s a good option if you’re concerned about low supply but want to keep breastfeeding as the primary method. If the top-up is temporary and you want to return to exclusive breastfeeding, pumping after or between feeds helps maintain your supply signal.
Preventing Bottle Preference
Newborns can develop a preference for bottles because milk flows faster and more consistently from a bottle nipple than from a breast. Paced bottle feeding is a technique designed to prevent this by mimicking the rhythm of breastfeeding. It slows the feeding rate and extends meal duration so your baby has to work for the milk in a way that feels more like nursing.
The basics: hold your baby in an upright or semi-upright position rather than reclined. Use a slow-flow nipple. Hold the bottle nearly horizontal so milk doesn’t pour out by gravity. Let your baby draw the nipple in rather than pushing it into their mouth. Pause every few minutes by tilting the bottle down or gently removing it, then let your baby signal they want more. A formula feed should take roughly as long as a breastfeed, around 15 to 20 minutes, not five.
What Changes You’ll Notice
Once formula enters the picture, your baby’s stools will change. Exclusively breastfed newborns typically produce loose, seedy, mustard-colored poop. Formula-fed stools tend to be firmer (though still soft, roughly the consistency of peanut butter), more tan or greenish in color, and more predictable in frequency. Breastfed babies can go anywhere from several times a day to once a week and be perfectly healthy. Formula-fed babies most often poop about once a day. With combination feeding, expect something in between.
You may also notice your baby takes slightly longer to digest formula feeds, since formula proteins break down more slowly than breast milk proteins. This can mean your baby goes a bit longer between feeds when formula is involved.
What Your Baby Still Gets From Breast Milk
Even partial breastfeeding delivers components that formula can’t fully replicate. Breast milk contains over 100 types of human milk oligosaccharides, complex sugars that your baby can’t digest but that feed beneficial gut bacteria, particularly Bifidobacterium species. These sugars are the third most abundant component of breast milk after fat and lactose, and they help establish your baby’s microbiome while blocking potential pathogens.
Breast milk also delivers antibodies, with secretory IgA making up 90 to 95 percent of the immunoglobulins present. These antibodies bind directly to bacteria, viruses, and toxins in your baby’s intestine. Colostrum, the milk produced in the first few days after birth, is especially concentrated with these protective proteins. So even if you plan to rely heavily on formula later, breastfeeding in those early days provides an outsized immune benefit.
Vitamin D for Mixed-Fed Babies
Breast milk is low in vitamin D regardless of your own intake, which is why exclusively breastfed babies need a daily supplement. You might assume that adding formula (which is fortified with vitamin D) covers this gap, but the recommendation for combination-fed infants is still 400 IU of liquid vitamin D daily. Unless your baby is drinking roughly 32 ounces of formula per day, which a newborn won’t be, the formula alone isn’t enough to meet their needs.