Mother and Baby

How to store breast milk and the best milk storage bags

Section: Feeding
Breast milk storage bags

When you've spent so long expressing your breast milk, you want to preserve every single precious drop for your baby. And the main way of doing this is by pumping and storing breastmilk, whether that's refrigerated or frozen, in breast milk storage bags or bottles. 

We've broken down everything you need to know about breast milk storage and the best breast milk storage bags that'll make the journey from boob to your baby's mouth a lot simpler, saving that 'liquid gold' and you that time and stress in the process. 

The benefits of storing breast milk

  • So your partner can help with feeds.
  • If you're unable to breastfeed because you're at work or otherwise engaged.
  • To relieve the pressure of sore breasts and nipples.
  • If you're power pumping to boost your milk supply.
  • If your baby is struggling with latching but you would like to feed your baby with breast milk.

Can you freeze breast milk?

If you want to keep your breast milk for longer, you can freeze it for up to six months but you must use it up within 24 hours after defrosting.

How to store breast milk

It's quick and simple to store your freshly expressed breast milk. Here's what to do for safe storage...

1. Wash your hands before handling the breast milk.

2. Pour your milk in sealed and sterilised bottles or breast milk storage bags. If you’re going to freeze the milk, leave a couple of centimetres of air space at the top as the liquid will expand when frozen.

3. Store the milk in small amounts so as to avoid waste. This will mean it will warm or thaw quickly.

4. Label and date your milk with the date and time that you expressed the milk.

5. After ensuring it is secure, pop the milk in your fridge or freezer.

Breast milk in storage bags

How long can you store breast milk in storage bags?

It's best to check with the breast milk storage bag manufacturer for their recommendation, but don’t worry if you’re out and about as your expressed breast milk is fine to stay at room temperature for about six hours. However, any longer and it should be in a fridge.

Your milk can be stored in the fridge for up to five days at 4 degrees celsius or lower or for two weeks in the ice compartment of a fridge. You can buy a fridge thermometer from a kitchen shop if you are unsure of the temperature.

Use the oldest stored breast milk first providing it is still within its use-by limit.

Defrosting frozen breast milk

When it's time to defrost your breast milk, you ideally want to do it slowly in the fridge which could take up to 12 hours. However, if you do need to use it immediately, you can defrost it by popping it in a jug of warm water or by holding it under warm running water.

Once the milk is defrosted, give it a gentle shake if it has separated and use this straight away. Do not re-freeze milk that has been defrosted.

Best breast milk storage bags

Super easy when it comes to transporting and pouring, these leak-proof bags have secure seals and standing bases so there's no need to worry about losing any of your milk. The unique shape provides an easy pour spout, and each bag comes BPA-free and pre-sterilised to save you extra faff.

Bronze winner of the Best Product for Breastfeeding (excluding breast pumps) for the 2020 Mother&Baby Awards. Read our full review.

Review: "My favourite breast milk bags! I prefer them to the bigger brand ones. You can fit more milk in which is great for my hungry baby who takes a big feed. The seal is really nice and secure and the bags are strong. The pouring bit makes transferring the milk to the bottle easier and safer from spillage. I’ve just ordered another box as I’m so impressed."

Specially designed so that your breast milk can safely be stored in both the fridge or freezer, these bags are pre-sterilised, BPA, and BPS free so no harmful substances can contaminate your stored breast milk. Plus, you can now pump directly into the bag using any Lansinoh breast pump - super handy for instant storage or carrying breast milk on the go. There are 50 bags in each box. 

Bronze winner of Best Product for Breastfeeding (excluding breast pumps) in the 2021 Mother&Baby Awards. Read our full review. 

Our mum tester Catherine Lovell said: "These breast milk bags have been really handy in beginning my stash of frozen breast milk for when I go back to work. You get a large amount of bags in the pack, so you won't run out in a hurry! They are quick and easy to use. They have a bottom which allows them to stand up in the fridge and a label at the top where you can write the date and amount etc."

Each of these ASDA storage bags is sterilised, BPA free, and has a stable base, allowing you to stand it upright. They also have a double seal so there is no worrying about any leakage in the fridge or freezer and at under £5, we love the price too. It's a great affordable option, without compromising on quality.

Shortlisted for Best Bottle Feeding Product in the 2020 Mother&Baby Awards. Read our full review. 

Our mum tester Katie said: "I would recommend this product to any fellow breastfeeding mums so it easily enables them to freeze and feed baby from the bottle with their own milk. The top enables you to pour the milk very easily into the bag without it spilling. They are very slim and also made of thick plastic so very durable to use in the freezer."

The Closer to Nature Milk Storage Bags from Tommee Tippee are pre-sterilised allowing you to simply pour expressed milk directly into the bag, and come double fastened at the top of the bag to ensure that none of that precious breast milk can leak or escape. The bags can stand on their own thanks to the gusseted base, and can be easily labelled so you can keep track of the date they were added to the fridge/freezer.

Review: "I was expressing for twins and found that other storage bags didn't hold more than around 7oz. These bags hold so much more. I loved the fact they can be stored upright to save space and more importantly that they stay upright when placed in the fridge. The double seal means I haven't had a single one leak."

Boots own-brand breast milk storage bags are pre-sterilised, easy-seal, and come with double walling for extra strength. Specially designed with a zip closure to prevent leaks, these bags will keep your milk safe and sterile for feeding.

Each of the bags arrives pre-sterilised, and features a write-on tab so that you can make a note of the date to ensure your baby enjoys the freshest, nutrient-rich milk. They're leak-proof, free-standing, BPA free, and with an improved oxygen barrier, these bags will keep your milk fresher for longer.

Review: "Great item, looks strong, and proper seals on the bags."

Another pack of 50, meaning you'll never run short, the Medela Breast Milk Storage Bags are ready-to-be-used, making storing, transporting, and warming your breast milk super convenient and hygienic. The food-grade, BPA-free bags have heat-sealed seams that prevent them from tearing, and a large area for easy labelling and dating.

Review: "Great quality, thick bags with a good seal. Easy to fill using the breast shield as a funnel."

We love the innovative design of these breast milk storage bags that are flat, single-use (you can buy more bags separately), pre-sterilised and are designed to cool and warm contents twice as quickly as bottle storage for optimal preservation of your milk's nutrients. They're durable and leak-proof, and the fantastic organiser provides a space-saving solution that helps you track pumping order and maintain a 'first in, first out' policy.

Review: "The whole nanobébé system is about preserving the nutrients in breastmilk and these storage bags are great for building up your reserves in the fridge or freezer."

Is it safe to store breast milk in plastic bags?

Yes, so long as they are BPA-free. Breast milk storage bags have been specifically made to store breast milk and so will always be safe and hygienic to use, as well as more robust to keep your valuable breast milk contained.

Can you wash and reuse breast milk storage bags?

Most breast milk storage bags available, and all of those on our list, are single-use and so should only be used once to prevent any risk of cross-contamination. 

In fact, there are minimal reusable breast milk storage bags online, with the only ones of note available from US retailer Junobie.

They claim to have the first eco-friendly and reusable breast milk storage bags, and made of 100 per cent silicone, they're dishwasher, freezer, and steriliser safe for cleaning and reusing time and time again. 

However, if you're planning to freeze breast milk often, these aren't the most cost-effective solution, making single-use breast milk storage bags the easier, more accessible choice.

Is it better to store breast milk in bags or bottles?

If you're planning to store expressed breast milk for a long while, breast milk storage bags are ideal as a space-saving storage solution as you can neatly and easily fit the bags in your fridge and freezer.

However, if you only plan to express milk to use in a matter of days, a bottle may be preferable for easy, instant feeding. If you're looking for a reusable option, too, saving on single-use plastic, you might prefer to use a bottle as it's easier to find.

Popular reads:

  • Author: Emily Thorpe Emily Thorpe
  • Job Title: Digital Writer

Having written for Mother&Baby magazine for four years where she wrote news, product pages, features and interviewed celebrities such as Paloma Faith and Fearne Cotton, Emily now works as Digital Writer for Mother&Baby online where she specialises in travel and product reviews. 


Other contributors

Eleanor Weaver - Commercial Content Writer

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