When it comes to the well-being of your child, nothing beats being informed.

Whether you are breastfeeding, formula feeding or are somewhere in between, it always feels good to know that you’re doing the right thing by your baby. But sometimes, you might find yourself battling confusion, as you ponder questions that have gone unanswered such as whether or not you should mix formula and breastmilk for formula feedings at night.

Thankfully, we’ve got the answers you need to give you peace of mind. Whether you are dealing with a low supply of breast milk, are going back to work or your partner wants in on the fun, we’ll get you filled in so that you can decide whether or not mixing formula with breast milk is the right option for you.

Can I Mix Formula With Breast Milk?


In fact, mixing breast milk with formula is one of the best ways to introduce formula to your baby’s diet for more reasons than one. Not only will your breast milk help your baby to digest the formula you are introducing, but mixing formula with breast milk can also be ridiculously convenient.

Don’t believe us? Check out a few of these scenarios that will open your eyes to how combining formula with breast milk can make things easier than ever!


Is It Safe to Mix Breast Milk and Formula?

At this point, you may be pondering the safety and effectiveness of mixing formula with breast milk for your baby. After all, with all of the wildly concerning trends circulating the internet these days, you may be wondering if this concept, though convenient, is actually a healthful alternative to aid in your baby’s diet.

Thankfully, if done correctly, mixing breast milk with formula is, indeed, safe.

Remember when your post-partum care team kept referring to your breast milk as “liquid gold”? They weren’t kidding! Packed with antibodies and a multitude of nourishing nutrients, breast milk can actually aid in better digestion of whichever formula you choose to offer your little one.

Nevertheless, there is one tiny caveat to this statement.

When mixing breast milk and formula in the same bottle, it is very important that you take special care to prepare the formula according to the package directions.

If you are using a ready-to-feed formula variety, you can simply add your breast milk to the formula without concern.

However, if you are using powdered or liquid concentrate, you’ll need to prepare the bottle according to the package directions first, and then add your breast milk.



Because by adding your breast milk without diluting the concentrated liquid or powder first, you run the risk of providing your baby a little too much in the way of nutrients and nourishment. The outcome will be an influx of vitamins that will do a number on your baby’s delicate kidneys.

If you’re a new mum, we understand that much of the journey towards caring for your baby can be stressful and vexing. Check out this article on combination breastfeeding to help alleviate many of the common woes associated with mixing formula feeding and breast feeding in the beginning.


Mixing Breast Milk and Formula Together

The following are the most common methods for mixing breast milk with formula for babies:

  • Nurse First and Then Offer a Formula Bottle
  • Offer a Bottle of Breast Milk First and Then a Separate Bottle of Formula Milk
  • Mix Both Formula and Breast Milk in the Same Bottle
  • Alternate Breast Milk and Formula Throughout the Day


Mixing Breast Milk and Formula in the Same Bottle

When it comes to the question: “Can I mix formula and breast milk in the same bottle?” the answer is a resounding yes. Nevertheless, there are a few things we hope you’ll consider before doing so.

First, we know how precious the breast milk you’ve worked so hard for can be, and as such, you’ll likely wish to conserve as much of it as possible. Thus, it is important to note that mixing breast milk and formula in the same bottle may potentially lead to you wasting some of your breast milk.

The reason? If your baby is unable to finish his or her bottle, that breast milk mixed with formula may go to waste. If you are gung-ho about preserving as much of your breast milk as you can, you may want to opt to feed your baby breast milk and formula, separately. Breast milk first, then formula.

On the other hand, if you’d like to get your baby fed in one step and don’t wish to fuss with multiple bottles, the winning choice is to go forth with a breast milk formula mix in a single bottle. To further curb waste, you may want to put the breast milk and formula in separate bottles the first couple of weeks, and then, if he or she is consuming the entire bottle, go ahead and transition to mixing breast milk and formula in same bottle.


Can You Mix Cold Breast Milk With Formula?

When mixing breast milk and formula, you don’t have to ensure that the breast milk is any particular temperature, outside of scorching hot, for the mixing magic to happen. In this case, you can, indeed, mix cold breast milk with formula as long as you are following the package directions before doing so.

Remember, you should never mix breast milk with any undiluted concentrate.

Although not necessary, if you’d like to warm your formula mixed with breast milk, go ahead and do so using a gentle method. We recommend using a bottle warming, running an already mixed bottle under hot water for a few minutes, or gently warming the milk over the stove. You could even nix the warming process all together to give your baby a refreshingly chilled treat.

The choice is entirely yours!


Does Mixing Breast Milk and Formula Cause Constipation?

As previously mentioned, breast milk acts as a nourishing and nutritious agent that aids your little one’s body in digestion. As such, if anything, your baby will likely react better to receiving breast milk combined with formula than they will to having formula on its own. If you found that your baby was reacting negatively to formula to begin with, you may want to give mixing breast milk with formula a go, as doing so will likely help to minimize tummy issues.

But what if your baby does experience constipation, when they previously had not, after the introduction of breast milk in their formula? Honestly? It probably isn’t the breast milk.

Instead, it is more likely that your baby is experiencing gastric issues due to another cause, like illness. We understand that it can sometimes be tricky to determine the exact cause of these types of issues. The solution? Be prepared. To help with this, you may consider purchasing a baby essentials kit packed with equipment like a thermometer, emergency teether and more, to soothe your baby’s various ills no matter where you are.


The Bottom Line…

Combining formula and breast milk is totally safe, and is even recommended. Want a second opinion? Always ask your paediatrician for advice pertinent to your baby and his or her specific needs.

All in all, whether breast-fed, formula fed or somewhere in-between, the ultimate goal is that you have a happy, healthy and well-satiated baby, whose tummy stays full throughout the day.

So, great job, mum! Our hats are off to you!

Learn more about supplementing breast milk with formula and breast milk vs formula on our blog.