Combination feeding — also called combo feeding or mixed feeding — means your baby gets both breast milk and infant formula [9]. It can mean breastfeeding at some feeds and giving a bottle of formula at others, topping up a breastfeed with formula, or giving expressed breast milk and formula from bottles.
There is no single right version of it. Some families breastfeed almost exclusively and use one formula feed at night. Some formula feed almost exclusively and breastfeed once in the morning. Most sit somewhere in between and shift over time.
More common than the word "exclusive" suggests. In the United States, 86% of babies born in 2023 were breastfed at some point, but only 48% were still exclusively breastfed at three months and 30% at six months [2]. Among breastfed babies, 23% had already received some formula before they were two days old [2]. Most breastfed babies in the US therefore get some formula in their first six months.
And most mothers who stop breastfeeding did not plan to stop when they did. In a US cohort followed for a year, about 60% of mothers who stopped said they stopped earlier than they wanted, most often because of lactation problems, worries about the baby's nutrition or weight, illness or medication, or the effort of pumping [1]. Combination feeding is often the option that would have let them keep going.
The American Academy of Pediatrics recommends exclusive breastfeeding for about six months, then continued breastfeeding alongside solid foods for two years or beyond "as long as mutually desired by mother and child" [4]. The World Health Organization's position is the same [11].
The same AAP statement also says: "Exclusive or any breastfeeding is not always possible, despite the best of intentions, and these mothers and families need special support" [4]. The recommendation is a target, not a pass/fail test.
The reason exclusive breastfeeding is recommended over mixing is mainly about supply. Breast milk is made on demand. Every breastfeed that is replaced by formula, especially in the first weeks, tells your body to make less [9] [10]. In a study of first-time mothers who intended to breastfeed exclusively, those whose babies got formula in the hospital were about twice as likely not to be fully breastfeeding at one to two months, and nearly three times as likely to have stopped by two months [7]. That is an association, not proof of cause — mothers who were already struggling were more likely to supplement — but it is why midwives push back on early top-ups.
A randomised trial tested the opposite idea: giving small, structured amounts of formula to newborns who were losing weight, to see whether it would help mothers keep breastfeeding. It did not improve breastfeeding rates at six or twelve months, and did not clearly harm them either [8]. The honest summary is that early formula does not help supply, may hurt it, and the effect depends heavily on how it is done.
If you want to protect breastfeeding, the usual advice is to wait until it is well established, which for many people is around six to eight weeks [10] [6]. USDA's WIC programme puts it as: do not start combination feeding "until you are breastfeeding regularly and well" [9].
If you need to supplement earlier — because your baby is not gaining weight, because of a medical reason, or because you are exhausted — that is a conversation for your paediatrician or midwife, not a reason for guilt. The goal is a fed, growing baby.
Mothers who supplement report more guilt and less satisfaction with feeding than mothers who breastfeed exclusively — in one survey of 845 breastfeeding mothers, guilt and dissatisfaction were higher among those using any formula, regardless of what they had originally intended [3]. The researchers' conclusion was not that these mothers were doing something wrong, but that the way breastfeeding is promoted leaves too little room for the many who end up mixing. If that is you, see breastfeeding guilt.
Keep breastfeeding or expressing at the feeds you want to protect, and replace one feed at a time with formula, waiting a few days between changes so your supply adjusts. Give the first bottles when your baby is calm rather than very hungry, and keep skin-to-skin contact. Express at any breastfeed you drop if you want to keep that milk.
Yes. Any breast milk your baby gets counts. In the US, 86% of babies born in 2023 were breastfed at some point but only 30% were exclusively breastfed through six months, so combining is the most common real-world pattern.
Health bodies recommend exclusive breastfeeding for about six months because milk supply works on demand — every formula feed that replaces a breastfeed signals your body to make less. Studies of first-time mothers show early formula top-ups are linked to stopping breastfeeding sooner. It is a recommendation about protecting supply, not a rule that formula harms babies.
If exclusive breastfeeding is not working for your body, your baby or your life, combining is a reasonable middle path that keeps some breast milk in your baby's diet. Waiting until breastfeeding is established (often around 6–8 weeks) and introducing formula slowly protects your supply best.
Official guidance from the CDC and NHS does not cover mixing them in one bottle. If you do, make the formula with water exactly as the tin says first, then add expressed milk, and treat the whole bottle by the stricter formula rules: use within an hour of starting the feed and throw away what is left.
Start with one bottle a day at the feed you most want to replace, ideally given by someone else while you are out of the room. Use a slow-flow teat and paced feeding. Wait three to five days before replacing a second feed.