Storage

How to freeze, label and store breast milk

By the Little Stash team · Updated 19 October 2026 · 2 min read

Freezing breast milk well means less waste and less worry. A few simple habits make it easy to find the right bag, use the oldest milk first and stay within NHS storage times.

What you need

• Sterilised bottles or breast milk storage bags made for freezing.
• A permanent marker or labels that stay on in the freezer.
• A freezer at -18°C or colder. A cheap freezer thermometer tells you for sure.
• A box or tray to keep your stash together and in date order.

Bags or bottles?

Storage bags take up less space and freeze flat, which suits a big stash. Bottles are sturdier and reusable but bulky. Many mums use bags for the freezer and bottles for milk that will be used from the fridge within a few days.

How to freeze breast milk, step by step

1. Wash your hands and use a sterilised pump and container.
2. Pour in a small portion. 60 to 120ml per bag is a good size, so you only defrost what your baby will drink.
3. Leave space at the top. Milk expands as it freezes.
4. Squeeze out the air and seal the bag.
5. Label it with the date you expressed it and the amount in ml.
6. Lay bags flat in the freezer until frozen, then stand them upright in a box like files. They thaw faster and take up less room.

What to write on the label

• The date it was expressed. This is the date that counts for storage times, not the date you froze it.
• The amount in ml.
• Your baby's name, if the milk is going to nursery or a childminder.

How long it keeps

NHS guidance says expressed breast milk keeps for up to 6 months in a freezer at -18°C or colder, up to 2 weeks in the ice compartment of a fridge, and up to 8 days at the back of a fridge at 4°C or colder. See the full UK breast milk storage guide for every situation.

Keep your freezer stash organised

• Store bags in date order and always take from the oldest end.
• Group bags by week or month with an elastic band or separate boxes.
• Keep a running total so you know how much you have without counting bags.
• Check the dates every couple of weeks so nothing goes past 6 months.

Defrosting safely

• Defrost slowly in the fridge, or faster in a jug of warm water.
• Once defrosted, gently swirl it if it has separated and use it straight away.
• Never refreeze milk that has been defrosted.
• Never warm breast milk in a microwave or on the hob. It can cause hot spots that burn your baby's mouth.

Common questions