Can you mix together warm and cold breastmilk? Answered!

Moms are super busy, especially when juggling pumping and feeding schedules! Being able to mix freshly expressed breastmilk (ie, what you just pumped) with chilled breastmilk is extremely convenient. 

It’s why so many moms are fans of the pitcher method. This method involves pooling the breast milk you pump into a single container, which is kept in the refrigerator. Then, the pooled milk is poured into individual bottles for feeding – or dispensed into freezer bags to be used later.

But this also begs the question, “Is it okay to mix breastmilk of different temperatures together?” In fact, it’s the MOST common question about the pitcher method we get!

So, what’s the answer? 

Whether or not you can mix fresh breast milk with chilled milk has been a hot debate over the years. For example, here are what some of the top sources have to say on the issue:

1: The Center for Disease Control (CDC) advises not to pool the two temps together. The theory (based on how typical food reacts) is that pouring warm milk into chilled milk will allow bacteria to grow. You can read more about their statement and advice here. 

2: Recently, the American Pediatric Association (APA) actually RECOMMENDED that pooling warm and chilled breastmilk as a way to make breastmilk storage more efficient. As part of their Frequently Asked Questions, the APA site stated: “Mothers can mix warm milk and cold, or even consider pooling milk from 24 hours together, which may help even out variability in nutrients due to pumping time or breast emptying (which influences fat content of the milk).” Later, they removed that statement from their site without further explanation. 

3: Infant Risk is widely recognized as a trusted source for information on human milk. In a recent update, they addressed the topic of mixing freshly pumped milk with refrigerated milk. Previously, it was advised to cool freshly pumped milk before adding it to a pitcher. However, new guidance suggests that this step is unnecessary. According to Infant Risk, freshly pumped milk can be combined directly with refrigerated milk, provided that each pitcher is used for milk collected within a 24-hour period. 

What should a mom do? 

So, given the varying advice, what should a mom do? Here are 4 tips to help you make a decision within your own home. 

1: Take comfort in what lactation consultations say

Most lactation consultants and pediatricians acknowledge that breastmilk is naturally antibacterial and therefore isn’t prone to issues with mixing the temps during a 24-hour period. If you don’t feel sure, ask your consultant or doctor for their opinion!

2. Follow the 24-hour rule

Many moms pool breastmilk over the course of several days. That’s because you can technically keep breast milk in the fridge for up to 4 hours. However, a safer course of action is to only pool milk for 24 hours. 

After 24 hours, you’ll want to use or freeze what you’ve pooled and start with a fresh batch. That’s why we recommend having two pitchers in the rotation. It helps save time as you rotate them out each day. Generally, you can handwash your pitchers. When it comes time to sterilize them, the CDC recommends putting the pitcher in a pot and filling it with cool water. Then, bring to a boil. Boil for 5 minutes. Then safely remove with tongs and air dry.

3. Take precautions when needed

Even though milk does not need to be cooled before mixing, it’s essential to maintain good hygiene to avoid contamination. Always wash your hands and ensure all equipment is properly sterilized.

It’s also important to note that some babies have weakened immune systems due to premature birth or other health concerns. In those cases, it’s always best to follow the most stringent recommendations for breast milk storage safety, which includes not mixing temperatures.

4. Follow your mama’s intuition

Mother’s intuition is an amazing thing. When in doubt, ask the experts for their advice, and follow your gut. Most moms feel comfortable mixing temperatures, but follow what makes you feel most comfortable and what works best for the routines of your family.

Want to keep up with what the experts say about mixing breast milk temperatures? Follow Nestberry on Instagram! We like to keep up with the latest advice and share it with our community, along with other breastfeeding and pumping tips and tricks!

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