How to Handle Mixing Formula and Breastmilk

Some women start thinking about supplementing breastmilk with formula when they need to get back to work when their milk supply is too low, and baby is not getting enough to eat or when they need to get their partner involved in those night time feedings. No matter the reason, the questions will always be the same. Is it okay to do so? Will it affect the milk supply? How can I make sure my baby gets the best of everything?

All lactation specialists recommend supplementing with formula if your milk supply is low or if you need to get back to the office and pumping is not an option. This is because even some breastmilk is better than none, and because the body can also adapt to producing milk for a limited number of feedings.


Baby, Health, Safety

If you’re asking if you can supplement breastmilk with formula to satisfy your baby’s appetite, then the answer is yes. But, if you’re looking to actually mix formula and breastmilk together in the same bottle, that’s usually a no-no.

For starters, your baby may not eat the full bottle. This means your precious milk is going to waste if it is mixed with the formula. A good idea would be to prepare two ounces of formula in a different bottle and give it to your baby once he has finished eating from the breast.

Another reason why you should never mix the two in the same bottle has to do with storage. The formula must be thrown out in a couple of hours after it’s mixed, while breastmilk does not spoil as quickly.


If you choose to give formula and breastmilk, it doesn’t mean you’ve given up on breastfeeding altogether. It just means you may need a break or that your baby needs more to eat than you can give.

Giving formula and breastmilk has its benefits. Doing so allows mom to get some much-needed sleep during the night if someone else is doing a bottle feeding at 3 a.m.

If your baby is a bit older and you are thinking about weaning, then giving formula and breastmilk is an excellent way to help him ease into this transition. An excellent way to start is to cut feeding during the day. You don’t want to stop cold turkey at the risk of engorgement issues on your end. You want to slow down your milk supply so that your baby doesn’t depend on you 24/7 for all of his nutritional needs.

Baby, Health, Safety


One of the primary reasons many moms decide to supplement with formula is when they are preparing their baby to go to daycare. Unless you have a freezer full of breastmilk, you’ll need to give your baby formula. It’s best to do this before your baby actually starts daycare. The last thing anyone needs is a fussy baby crying for mother’s breast when mom is not around. A good idea would be to skip the breastfeeding sessions in the same hours you expect the baby to be away from you. This way you can get him on a schedule.

Baby, Health, Safety

It is important to remember that this is best done after baby’s first 8 weeks. This will help your body get on a breastfeeding schedule and help you keep up with your baby’s needs. If you intend to wean because you need to get back to work, try to keep some breastfeeding sessions at the beginning and at the end of the day. Your body will reduce milk production, but baby will still get much of that needed immune system boost which he can only get from mother’s milk.


No matter how many times doctors may say that giving formula and breastmilk is fine, mothers may still have their doubts. Do mixing formula and breastmilk cause gas? Will I get a colicky baby? Do you add water or can you mix formula with breastmilk? Will baby suffer from constipation or diarrhea? Here are some answers that will help.

  • First, some changes in digestion can be expected as the diet diversifies. Typically, a baby who is only breastfed will have up to six runny, mustard-colored bowel movements. The introduction of formula should make the bowel movement harder and darker in color. Like with any change, some babies can get gas; others can have difficulties passing their stools and can become constipated. If this is an issue, ask the pediatrician. He may recommend another type of formula that will agree with baby more.
  • If your baby gets diarrhea and there is mucus or blood in the stool, or if there is cramping, severe bloating and gas, there’s a chance your baby is lactose intolerant. Formulas contain lactose, the milk protein that causes the intolerance. Check with your doctor about possible alternatives.
  • Don’t mix formula with breastmilk directly. If you do, the result will be a liquid that’s too concentrated for baby to stomach. Add water instead to make formula.


The main side effects of mixing formula and breastmilk are:

  • A decrease in the milk production by the mother
  • Babies growing attached to the bottle since the nipple releases more milk more efficiently

Since a newborn is still learning to latch on, introducing a bottle may make it harder to get them to go back to the breast because they can get milk from the bottle more easily.

Always consult with your doctor if you are concerned about your baby’s feedings. He or she can work with you to find the best way to give formula and breastmilk that works for you and your baby.


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