Combination feeding: breastfeeding and formula together

There is a version of infant feeding that does not make it into many of the books: the one where some feeds are at the breast and some are from a bottle. Maybe you're going back to work. Maybe you're exhausted and need someone else to do the 3 am feed. Maybe breastfeeding has been difficult and you want to protect your baby's health without abandoning what's working.

Combination feeding — mixing breast milk and formula — is extremely common, and it works. Understanding the mechanics helps you do it in a way that supports your goals rather than undermining them.

What combination feeding is

Combination feeding means giving a baby both breast milk and infant formula, in any proportion. This might look like:

• Breastfeeding most feeds, with one or two formula feeds per day
• Breastfeeding in the morning and evening, formula during the day with a childminder
• Expressing breast milk for some feeds and supplementing with formula when supply is short
• A gradual shift from mainly breastfeeding toward mainly formula as circumstances change

There is no single correct way to do it. The approach should fit your situation.

Why families combination feed

The reasons are varied, and most of them are good reasons:

• Returning to work and unable or unwilling to pump enough to cover all feeds
• Low milk supply that cannot meet the baby's full needs — formula fills the gap without stopping breastfeeding entirely
• Medical reasons for the baby — some newborns need supplementation for jaundice, low blood sugar, or weight concerns in the early days
• Rest and shared care — a partner or family member doing some feeds
• Personal preference — simply wanting to do both

Any amount of breastfeeding carries immunological benefit for the baby. The WHO recommends breastfeeding for up to 2 years and beyond, and notes that partial breastfeeding still provides protection.¹ This is not a competition with an all-or-nothing outcome.

The effect on supply: timing matters

This is the most important practical point. Breast milk supply is regulated by demand: the more milk that is removed, the more is produced. When a formula feed replaces a breast feed, the breast receives no stimulation for that feed, and over time, supply adjusts downward to match the reduced demand.

In the first 4–6 weeks, supply is still being established. Introducing formula feeds during this window without also pumping or expressing at the same time sends a clear signal to your body that less milk is needed. This can make it difficult to maintain the supply you want.²

After supply is established — roughly after 6 weeks, though this varies — most people find they can introduce one or two formula feeds per day without a significant effect on supply. The body adapts, but it adapts around a new lower level of demand.

The practical rule: if you introduce a formula feed, decide whether you want to protect the supply that would have been stimulated at that feed. If yes, pump or express at the same time as the formula feed is given. If you are intentionally reducing overall supply as you move toward less breastfeeding, you don't need to.

Preventing bottle preference

A baby who receives bottles regularly — whether of expressed milk or formula — can begin to prefer the bottle's faster, easier flow. This can make them impatient at the breast, where let-down takes a moment and flow is more variable.

Paced bottle feeding is the technique that mimics breastfeeding rhythm and slows the feed down. It involves:

• Holding the bottle horizontally (not angled steeply downward)
• Allowing the baby to open their mouth and take the teat rather than pushing it in
• Pausing every few minutes by tilting the bottle back so the teat empties, and waiting for the baby to signal they want more
• Ending the feed when the baby shows signs of fullness, not when the bottle is empty

This slows the feed and preserves some of the active sucking work that the baby does at the breast. It also prevents overfeeding, which is easier to do with a bottle than with the breast. For more detail, see the paced bottle feeding article.

Introducing formula: practical steps

If you're introducing formula feeds for the first time:

• Start with one formula feed per day. Choose a time that is least likely to affect supply — many people start with one evening feed, so a partner can help and the nursing parent can rest.
• Use a slow-flow teat. Regardless of the baby's age. Faster-flow teats make bottles so easy that breastfeeding becomes frustrating by comparison.
• Do not rush. Give your baby a few days to accept the formula and watch for any reaction before increasing the number of formula feeds.
• Watch your supply. If you notice a significant drop in supply and you didn't want one, add a pumping session at the time of the formula feed.

Some babies refuse formula outright at first, particularly if they have only had breast milk. Trying a different brand or a different temperature can help. Warming formula to body temperature tends to go down better than cold.

Maintaining breastfeeding alongside formula

If you want to keep breastfeeding as the majority of feeds:

• Protect the feeds that matter most to you — morning and evening feeds are often the ones nursing parents most want to keep
• Feed on demand at the breast whenever you are together and the baby is willing
• If you are pumping to replace missed feeds, try to maintain the same total number of stimulations (feeds plus pump sessions) as before
• Keep an eye on wet nappies and weight gain to make sure your baby is getting enough from all sources combined

Transitioning toward more formula

If you're moving gradually from mostly breastfeeding toward mostly formula — either by choice or because supply has declined — a gradual approach is easier on both of you:

• Replace one feed at a time, leaving at least a few days between changes to let supply adjust gradually
• Reduce the breast feeds that are already shorter or less productive first
• Allow your supply to reduce gradually rather than stopping abruptly — abrupt stopping can cause engorgement, blocked ducts, or mastitis

Complete weaning from the breast is a separate topic, but gradual is generally more comfortable than sudden.

Any breastfeeding is worthwhile

If you are combination feeding and wondering whether it's worth continuing to breastfeed at all, the answer — from an immunological standpoint — is yes. Each breastfeed provides antibodies, live cells, and bioactive components that formula does not. Even one or two feeds a day makes a difference. The WHO's position is that partial breastfeeding continues to provide significant protection against infection and illness.¹

This is not pressure to do more than is sustainable. It is just a factual counterweight to the idea that combination feeding is somehow second-best.

When to call your pediatrician

• Your baby is losing weight or not gaining adequately — they need to be getting enough from all sources combined
• Your baby is having fewer than 5–6 wet nappies per day
• You have signs of mastitis (a hot, red, painful area on the breast, possibly with fever) — this needs treatment
• Your baby refuses both breast and bottle and seems unwell

Tracking in PooPeeMilk

When you're managing both breast feeds and formula feeds, logging each one helps you see the full daily picture — how much total milk your baby is getting and from which source. PooPeeMilk lets you log breast feeds, expressed milk bottles, and formula separately, so you always have a clear record.

← Back to the complete guide: Breastfeeding: the complete guide

Also in this cluster: Pumping basics · Nursing strikes · Paced bottle feeding

Sources

1. World Health Organization. Breastfeeding. https://www.who.int/health-topics/breastfeeding
2. American Academy of Pediatrics. Breastfeeding and the Use of Human Milk. Pediatrics, 2022. https://publications.aap.org/pediatrics/article/150/1/e2022057988/188347/
3. NHS. Combined breast and bottle feeding. https://www.nhs.uk/conditions/baby/breastfeeding-and-bottle-feeding/breastfeeding/combined-breast-and-bottle-feeding/