Milk safety

If you find yourself pumping, you’ll need somewhere to store your breast milk.

Like many issues around breastfeeding, it can be difficult to figure out what you’re meant to do (and what you’re not). You may find you have questions about both the safety and the quality of your milk after storing.

In this section, we’ll break it all down for you.

Before we start, here are a few notes on our sources of information.

  • All the information we share below comes from the United States Center for Disease Control (CDC) or the research papers they refer to about milk safety. You can find their guidelines on storage and thawing of breast milk here.
  • The CDC recommends techniques for storing and preparing milk based on clinical guidelines developed by the Academy of Breastfeeding Medicine[1].
  • These guidelines are based on research for babies who are full-term and at home. If you find yourself in the NICU or your baby is pre-term, your healthcare team may recommend additional precautions.

What the guidelines say about milk safety

Ok, so how should you express, store, thaw and feed your baby safely according to the CDC guidelines?

It can help to think about it in steps:

  1. Preparing to express milk
  2. Storing your milk
  3. Thawing your milk
  4. Feeding your baby
Steps 1: Preparing to express

Before expressing, make sure you have washed your hands. If you are using a pump or re-usable milk storage bags, make sure they’re clean. You can find instructions from the CDC on how to clean and sanitise all your equipment here.

Step 2: Storing your milk

Pour your milk into clean, food-grade bags or containers. Make sure you use containers that are intended for breast milk. They should have tight fitting lids or seals, and they shouldn’t contain BPA (which can leach chemicals into the milk). Food-grade silicone options are great because they don’t contain plastic or BPA.

Label your milk with the date and amount (if it helps you plan, but not if tracking volumes is stressing you out).

As soon as you’ve finished expressing, you can store your milk for:

  • 4 hours at room temperature (e.g. on the counter)
  • 4 days in the fridge
  • 6 months in the freezer (although 12 months is also ok, but quality is best at 6).

When storing your breast milk in the freezer, make sure you keep it towards the back to avoid temperature changes from opening and closing the door.

Other tips that might help:

  • If you don’t think you’ll use within 4 days, it’s better to freeze straight away to maintain the quality of your milk.
  • Leave a couple of centimetres at the top to allow for milk to expand when it freezes
  • If you’re travelling, store your milk surrounded by ice packs in an insulated esky for up to 24 hours. You’ll need to find a fridge or a freezer as soon as possible after that!
Step 3: Thawing your milk

To thaw your milk, take the oldest out first (first in, first out) and either put in the fridge to thaw overnight or put in a container of lukewarm water. Don’t use the microwave as it can destroy nutrients and create hotspots which can burn your baby’s mouth.

If you’re thawing in the fridge, you need to use it within 24 hours from when it has thawed. If you’re thawing using warm water, you need to use it within 2 hours.

Never refreeze your milk after it has thawed. 

Step 4: Feeding your baby

In the movies, people heat milk and test it on their wrist before feeding to the baby. You don’t actually have to heat milk – cold or room-temperature milk is ok to drink!

However, you may find that it just seems nicer, and your baby seems to respond better to warmer milk. If you want to do that:

  • Place the sealed container (make sure it’s sealed) in warm (not hot) water. Never heat on the stove or in a microwave (see step 3 above).
  • Test the temperature on your wrist

Before you feed your baby, give your bottle a little swirl, to mix the fat (sometimes caked on the side) into the milk.

If your baby doesn’t finish the bottle, start your timer, and use it within 2 hours, or discard.

Don’t want to read through all of this again?

Below is a table from the cdc.gov website explaining the time windows to safely store your milk.

Guidelines are fine, but they don’t answer my questions

In practice, we follow the guidelines, but sometimes guidelines don’t contain the detail and tips that can make all the difference to your efficiency or stress when you pump.

Here are some extra tips that might fill in some gray areas you have questions about.

Can I put the pump in the fridge, in my cooler bag?

Yes. You don’t need to worry about damaging the pump in cold temperatures. The fridge is usually 3 to 6 degrees. Most pump manufacturers say their pumps should be stored between x and y. So, you’re good.

How to make sure your milk is safe to drink

  • how to pump - milk safety
  • how long can you keep pumped breast milk
  • how long can just pumped breast milk stay out
  • how long can my breast milk stay out after pumping
  • how long can pump breast milk stay out
  • how long can pump milk stay out
  • how long can pumped breast milk be left out
  • Can I put the pump in the fridge, in my cooler bag? Yes. Fridge is usually 3-6deg, most pump manufacturers say that their pumps should be stored between x and y. So you’re good.
  • Different milk colours 
  • pumping problem - hard lumps in breast milk
  • Freezer vs fridge
  • Use-by dates! 
  • Storage guide from Dr Milk

  • There's not actual evidence to support many of the recommendations commonly given in books and on websites in regards to breast milk handling and storage. The recs we make here are perhaps slightly more evidence based (when possible), experience based or common sense. Many of the milk handling rules commonly reported are derived from formula safety and arbitrarily applied to breast milk.
  • sniff/taste tests for any questionable milk is always wise. Spoiled milk is foul.
  • FORMULA (for comparison):
    • all formula should be discarded within one hour of baby starting to drink
    • ready to feed and concentrate liquid formulas are good after opening for 48 hours in the fridge
    • prepared powder formula is good 24 hours in the fridge
  • FRESH MILK:
    • In general, freshly pumped milk is good at room temp at least 6-8 hours, possibly up to 24.
    • Milk in the fridge is good 6-8 days. Extras can be frozen at any point. There may be some benefit for potential of longer term storage of frozen milk to freeze extras around the third day in the fridge. The bacterial nadir for refrigerated milk is on day 3.
    • It's fine to mix fresh pumped milk with cold milk in cooler or fridge. (Adding large volume of warm milk to frozen milk is not recommended.)
    • It's also generally considered safe to take a bottle out of the fridge and let it warm to room temp for a few hours before feeding.
    • The only exceptions may be moms with "high lipase" issues...the time in the fridge at which smell/taste issues appear varies widely. Scalding may be recommended by some (sooner than above time estimates) if baby refuses to drink the affected milk. There is no evidence to support the affects of "lipase" on refrigerated of frozen milk or to support scalding. Please ensure all other reasons for milk refusal are ruled out before starting to scalding all milk. The majority of bottle refuses are likely refusing the bottle, not the milk.
  • FROZEN MILK:
    • Frozen milk should be used within about 24 hours of complete thawing.
    • Milk can be stored in a regular freezer at least six months and in a deep freezer at least a year.
    • Milk doesn't magically expire on a certain day. It could get a little freezer burn or oxidize more and change the taste. I have used milk 18+ months in the deep freezer without issue and no signs of freezer burn. Even milk with a little freezer burn is still superior to formula. Published "limits" for length of freezer storage are because that's as long as the studies went. There is nothing that says frozen milk is "bad" after a certain date.
    • The less air in with the milk the less likelihood of freezer burn, oxidation, acquired freezer flavors, etc. Fill bottles almost completely leaving only small headspace, especially if long term freezing is expected. Squeeze all air out of bags before freezing. This is easier with some brands of bags than others.
    • It's ok to refreeze partially thawed frozen milk as long as ice crystals remain. This is true for all frozen foods, not just milk. It's a food safety issue, not specifically a breast milk issue.
  • LEFTOVERS:
    • All milk handling rules about discarding partial bottles and reusing milk are formula based and don't have much evidence to support any particular position. Because there are so many "if then" scenarios, this is a hard area to study. Those publishing guidelines therefore use an abundance of caution and give very conservative recommendations.