Combo feeding: combining breast milk and formula

By Kaya Thomas, founder of Milk Diary

Combo feeding, also called combination or mixed feeding, means your baby gets both breast milk and formula. Families do it for lots of reasons: a low supply, going back to work, needing a break, a doctor's advice, or simply because it works for them. Every feed counts, whatever's in the bottle.

This guide covers the ways to combo feed, how to mix breast milk and formula in one bottle, how to protect your milk supply, and what's worth tracking. It's not medical advice. Talk to your pediatrician or lactation consultant before you start, especially if your baby was born early, is under 2 months old, or has a medical condition.

Ways to combo feed

There's no single right way. Common setups include:

Can you mix breast milk and formula in one bottle?

Yes. Many combo feeding families mix them, and it's a simple way to give both in one feed. The order matters:

  1. Prepare the formula first with the right amount of water, exactly as the container says.
  2. Then add the breast milk.

Never stir formula powder or concentrate straight into breast milk, or use breast milk in place of water. That makes the formula too concentrated for your baby.

Once breast milk and formula are mixed, follow the storage rules for formula. If your baby often leaves some of the bottle, you can offer the breast milk on its own first and then a smaller bottle of formula, so less of your breast milk gets thrown out.

Batching breast milk when you combo feed

Formula and breast milk have very different shelf lives, so many parents like to keep them separate.

One way to do that is to pool your breast milk:

  1. Collect milk from each pumping session in one pooling container.
  2. Give formula-only bottles until you have enough breast milk for a full bottle.
  3. Pour a full bottle of breast milk from the pooling container into a fresh bottle, and keep pooling in that container for the rest of the day.

This allows you to leave a bottle at room temperature for overnight feeds for well term babies, or travel with a bottle of breast milk that's ready to go instead of mixing formula while you're out.

It's all about finding a system that works for you.

Preparing and storing formula safely

These rules come from the CDC:

Breast milk on its own keeps longer: up to 4 days in the fridge.

Protecting your milk supply

Your body makes milk based on how often it's removed. Adding formula doesn't automatically lower your supply, but if you nurse or pump less, your body will make less over time.

If you want to keep your supply up:

If you're happy with less breast milk, or you want to stop, that's a fine choice too. Your lactation consultant can help you cut back comfortably.

Bottle feeding a breastfed baby

A few things can help bottles go smoothly:

What to track when you combo feed

A log helps you and your care team see the whole picture:

There's no right ratio

Some families give mostly breast milk with a little formula. Others give mostly formula with some breast milk. Both are combo feeding, and both are a success. The best plan is one that feeds your baby and works for you.

Victoria Facelli, IBCLC, who advises Milk Diary, wrote Feed the Baby, an inclusive guide to nursing, bottle feeding and everything in between. It's a good next read if you're figuring out your plan.

Using Milk Diary for combo feeding

Milk Diary was built for every way you feed, including all of them at once:

Your data stays on your device and in your own iCloud. We can't see it, and there's no account to create.

Download Milk Diary free on the App Store

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