How to Store Expressed Breastmilk
Breastmilk is the best possible food to help your baby develop and grow. It contains antibodies, live cells and other substances to help protect your baby from infection and illness.
When you’re breastfeeding, it’s important to store your breastmilk safely to keep your baby safe and ensure they’re getting all the nutrients they need. Follow our guide on how to store expressed milk and learn how to safely heat it too.
How to store expressed milk
Breastmilk is suitable for storing due to its antibacterial properties, which help it to stay fresh and discourage the growth of bacteria.
When you’re expressing breastmilk, it’s particularly important to store your expressed milk in the right type of container to avoid contamination.
Breastmilk storage containers
Refrigerated or frozen milk should be stored in either sterilised hard-sided plastic or glass containers with well-fitting tops, sterilised BPA or BPS free containers, or breastmilk bags that are specifically designed for storing expressed milk, such as Lansinoh® Breastmilk Storage Bags.
It’s also important to mark the container with a date so you know how old it is and when to use it by.
Other storage tips:
- Wash your hands before expressing
- Wash your express milk pump and containers in hot, soapy water, rinse well, and allow to air-dry before use. Alternatively, you can wash and dry in a dishwasher
- Containers or bags should not be filled to the top – leave at least 2.5cm of space to allow the milk to expand as it freezes
- As well as marking the date on the container, also include your baby’s name on the label if your baby attends nursery or a childminder to avoid the milk getting mixed up with another child’s
- If you’re pumping and storing your breastmilk at work, make sure you label it with your name to avoid it getting mistaken for regular milk!
- Keep frozen breastmilk in the middle of the freezer where the temperature is most consistent. The temperature on the sides can fluctuate and if milk partially thaws, it can’t be refrozen
How long does expressed milk last?
When you’re expressing your milk to use at a later date, it’s important to refrigerate or cool it immediately to ensure it has the longest shelf life possible. The NHS states that when stored correctly, expressed milk will last for:
- up to five days in the fridge at 4C or lower
- two weeks in the ice compartment of a fridge
- up to six months in a freezer
They also advise that refrigerated breast milk can be carried in a cool bag with ice packs for up to 24 hours.
How to warm breastmilk?
Warming up breast milk needs to be done efficiently and carefully, especially if you are wanting to use frozen breast milk.
Heating breastmilk from frozen
If your milk is frozen, you can easily defrost it in the fridge, but remember to use it within 24 hours after defrosting.
Thaw and heat breastmilk under warm, running water, or in a bowl with warm or hot water. To preserve the nutrients in your milk, it’s important to not heat your breastmilk in a pan on the cooker. It’s also recommended to never heat your expressed milk in the microwave as it won’t heat the liquid evenly which could cause hot spots and hurt your baby.
If you need to defrost your milk more quickly, hold the container under a cool running tap and gradually increase the temperature of the water to heat the milk to a safe feeding temperature. Alternatively, immerse the container in a bowl of warm water. If the water has become cold before the milk has defrosted, take the milk out and reheat the water if necessary.
Once you’ve heated your milk, gently swirl the milk before testing the temperature. Mixing will also redistribute the cream into the milk as stored milk will separate into a cream and milk layer. Avoid shaking vigorously as it could damage some of the live components of the milk.
Can you reheat breastmilk?
We only recommend heating breastmilk once when thawed using the tips provided above, we do not suggest refreezing once thawed.
How much milk should I express?
To ensure you’re not wasting any breastmilk, store your expressed milk in 60 to 120ml (2 to 4 oz) quantities, at least until you know how much milk your baby consumes at each feed.
If you think your baby may need more, you can also store in smaller quantities of 30ml and combine with larger measurements.
To combine milk pumped at different times, first cool your fresh milk for 30 minutes in the fridge, then add the fresh milk to the frozen batch (only if there is less fresh milk than frozen). When using a mixture of milks pumped at different time, also remember to use it by the shelf life of the oldest expressed milk.
Why does my breastmilk have a soapy or rancid smell?
In very rare cases, some mothers may find that their milk smells soapy or rancid after storing. This happens when a mother produces milk that is high in lipase, an enzyme that breaks down fat in the milk. Depending the level of lipase, some mothers notice this rancid smell after their milk has been stored in the refrigerator; others notice it only after the milk has been frozen for a while and then thawed. Thankfully, this doesn’t happen often and can be prevented if the lipase is detected before the milk is frozen.
We suggest mums expressing milk test freeze some batches and thaw them after about a week to be sure they haven’t spoiled. If it does smell rancid when thawed, the milk can be scalded before freezing in the future to deactivate the lipase. For more information, refer to this article published by La Leche League International.
Most importantly, don’t forget that help is available! If you have any questions about breastmilk storage, speak to your midwife, health visitor or doctor for support.
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Please note: the guidelines on this page are recommended for healthy full-term babies. For advice on expressing milk for a premature or ill baby, please visit the Bliss website here.