There are many reasons mothers might want to express their breast milk.
They could have a premature baby that’s not well or strong enough to attempt breastfeeding.
Perhaps they’re due to go back to work and want to continue providing their expressed breast milk to their baby.
Or some mothers just want to have a backup supply in the fridge in case they’re away from their baby for extended periods of time.
Let’s look at breast milk storage and explore some facts and tips so you’re prepared to store breast milk if needed.
Breast milk storage guidelines Australia
The information about breast milk storage times in this article is based on the guidelines in Australia’s National Health and Medical Research Council’s infant feeding guidelines.
Human milk storage guidelines vary depending on what source is referred to.
Breast milk storage guidelines America
Guidelines for storing breast milk can differ in other parts of the world, such as America.
We’ve put together 14 of the most common questions and tips about breast milk storage.
#1: How long is breast milk good for at room temp?
If you’re regularly expressing breast milk using a breast pump and using the milk for the next feed, it’s best to leave the milk at room temperature.
You can leave freshly expressed breast milk at room temperature for up to 8 hours, as long as the room temperature isn’t above 26 degrees Celsius (78 degrees Fahrenheit).
If you live in a warmer climate, at temperatures above 26 degrees bacteria can start to form in your breast milk sooner, so 3-4 hours at room temperature is recommended.
How Long Can Breast Milk Be At Room Temperature? has more information.
#2: Can you refrigerate breastmilk after 4 hours?
Yes, you can.
Breast milk can be stored in the refrigerator safely for up to 72 hours. After this time it’s best to use the breast milk or freeze it.
The best storage location for expressed breast milk is at the back of the refrigerator. It’s the coldest area and better protected from temperature changes if the fridge is opened regularly.
#3: Can freshly expressed breast milk be stored in the freezer for 3 months?
There are different types of freezers so it’s helpful to know the best storage tips for your appliance.
- Breast milk can be stored in the freezer section of a refrigerator with one door for 2 weeks (at -15 degrees Celsius)
- A refrigerator with a separate freezer can store breast milk safely for up to 3 months (at -18 degrees Celsius).
- A stand-alone deep freezer that isn’t opened frequently can store breast milk from 6 months to -12 months (at -20 degrees Celsius).
Bear in mind, white blood cells are destroyed and vitamin C levels are reduced with freezing.
Total protein, fat, enzymes, lactose, most vitamins, antibodies, and other anti-infective factors are generally preserved, however, even in frozen breast milk.
#4: Can I mix breast milk from two different days?
It’s best to avoid adding freshly expressed milk to refrigerated milk.
To prevent any wastage, the best way to store your milk is in smaller amounts.
If you want to mix breast milk, to accumulate a larger amount, you can do it safely by adding cold to cold.
Make sure the breast milk is at the same temperature when mixing it, to prevent accidental warming of previously cooled breast milk.
#5: How will I know if breast milk is spoiled?
Did your baby have one whiff of your breast milk and turn his nose up? Did you have a taste and think it was a bit off?
If you’ve managed to follow the storage guidelines correctly then it’s most likely your milk isn’t spoiled.
So why does it smell or taste strange or your baby is refusing to drink it?
The cooling process can activate an enzyme in expressed milk, called lipase. This breaks down the fatty parts of the milk after it’s been stored.
Sometimes this can leave expressed milk smelling fishy, soapy, or with a strange metallic taste after it’s been stored in the fridge or freezer.
There’s nothing wrong with the milk, and in most cases, babies will drink it without a problem.
If your baby refuses to drink your milk, you can scald it before storing it to help prevent the lipase from activating.
Here’s how to do it:
- Heat the milk to 72 degrees Celsius for 2 minutes, right after expressing (before storing) to stop lipase from being activated
- Then cool the milk quickly, by putting the container into a bowl of ice and water
- Finally, store your breast milk as you like.
This process can reduce some of the protective factors of the cooled or frozen breast milk but it’s better than letting it go to waste.
#6: Can I warm breast milk in microwave?
Using a microwave to heat your breast milk is never recommended. It can cause hot spots and the milk might burn your baby’s mouth.
It also damages the properties of the expressed milk.
The very best way to heat your cooled breast milk is by placing it in a container of warm water, or under warm running water, until it’s heated just enough.
Frozen breast milk can also be thawed under warm running water.
The best place to test milk to make sure it’s not too hot is on your wrist.
#7: Can I put breast milk back in fridge after baby drinks from it?
It sounds gross but your little one has bacteria in his mouth, both good and bad. We all do!
This bacteria, though, can potentially get into the milk and contaminate it after a feed has started.
Although research is limited, it’s recommended to complete the feed and discard the remainder, or find another use for it. You can add it to the bath; it has lovely skin cleansing properties.
If you want to avoid wasting your precious milk, offer smaller amounts to your baby gradually until you feel he’s satisfied.
#8: Can babies drink cold breast milk?
It’s completely safe for your baby to drink breast milk cold from the refrigerator.
On a hot day, this could be quite refreshing.
Some babies will take their milk cold but some will prefer to have it at room temperature or warmed first.
#9: How long does breast milk last out of the fridge?
If you can, try thawing your frozen milk in the fridge before you use it.
If you need to use it more quickly you can defrost it out of the fridge.
It’s best to use it within 4 hours, though, as suggested by the Australian Breastfeeding Association’s article.
#10: Is it ok to store breast milk in bottles?
It’s completely fine to store expressed human milk in bottles, if you prefer.
The best way to freeze breast milk, however, is to use a plastic storage container or sealable bags.
Breast milk expands as it freezes, so leave some space for expansion in the container or bag.
Use breast milk storage bags or containers that are free from the chemical bisphenol A (BPA) for the best quality stored breast milk.
Avoid using disposable bottle liners to store freshly expressed breastmilk for long periods of time; this will prevent contamination from the plastic used in this product.
Try bags or containers that hold 1-4 ounce portions, to avoid wastage.
#11: Can I pump into the same bottle all day?
You can pump into the same bottle all day, providing you don’t add warm, freshly expressed milk to previously expressed room temperature milk.
In other words, you can use the same bottle as long as you remove the expressed milk from it and give it a rinse in running water before using it for the next pumping sessions.
#12: Can thawed milk can be stored in the fridge for up to 24 hours?
If you leave your pumped milk from the freezer to thaw in the refrigerator overnight, you should use it within 24 hours. Thawed breast milk shouldn’t be left at room temperature and then used in a feed.
#13: What happens if breast milk is left out too long?
There’s no good evidence related to re-freezing or re-cooling human milk expressed that isn’t used.
It’s best to follow the guidelines when handling leftover or unused breast milk, to ensure the best possible safety of infants and children.
There’s nothing to stop you using previously frozen milk left out of the refrigerator too long in a lovely moisturizing bath.
#14: Does expressed milk need to be discarded if I have a breast or nipple infection?
Freshly expressed breast milk is completely safe for your baby to drink, even if you have an infection.
Breast milk naturally contains healthy bacteria (probiotics), which are important to help establish a baby’s gut flora.
Probiotics create conditions in the gut that help stop the growth of unhealthy bacteria.