How to Store Breast Milk (UK): Fridge, Freezer, Cool Bag — NHS Times

You've just finished a pumping session, there's a bag of expressed milk in your hand, and you want to know, in plain numbers: how long does it keep? The NHS answer is clearer than parents sometimes think, and it's not the same as the American numbers you'll see on US blogs. Here are the current NHS times for every storage context, plus the rules for warming, thawing and giving cold milk.

The short answer: the NHS says freshly expressed breast milk keeps for up to 8 days at the back of a fridge at 4°C or colder, up to 2 weeks in the ice compartment of a fridge, and up to 6 months in a freezer at -18°C or colder. Milk that has been cooled in the fridge can travel in a cool bag with ice packs for up to 24 hours. You can feed expressed milk straight from the fridge if your baby is happy with it cold. After a feed, any leftover milk should be thrown away. Never re-freeze thawed milk, and never defrost in a microwave.

NHS storage times at a glance

Both of the NHS's pages on this — the expressing and storing breast milk page (reviewed August 2026) and the Start for Life storing breast milk page — give the same numbers. Quoting nhs.uk directly:

A few things worth knowing before you follow the numbers:

• "Back of the fridge" is not a decoration. The NHS specifies "at the back of the fridge – not the door", because the door is the warmest part and opens every time you reach in. Keep the stash furthest from the door.
• "Up to 8 days" is a ceiling, not a target. If you can use milk sooner, do. The 8-day figure assumes a reliably-cold fridge; if yours fluctuates, the NHS's 3-day rule applies.
• The ice compartment is the small freezer bit inside a fridge (sometimes called a "chill box" or "two-star compartment"). It isn't as cold as a dedicated freezer, which is why the time is shorter.
• "Cool bag" means 24 hours only if the milk went in already cold. Straight-from-the-pump warm milk doesn't get 24 hours in a cool bag — chill it in a fridge first.

Containers and bags

The NHS says expressed milk goes in "a sterilised container or in special breast milk storage bags". A few practicalities:

• Label every container with the date you expressed it, and (if you'll need it) your baby's name — handy for nursery or hospital. Use the oldest first.
• Cool fresh milk in the fridge before adding it to a frozen batch, so you're not warming what's already frozen. Treat the whole bag or bottle as "expressed on the earliest date" when you decide how long it keeps.
• Freeze in small amounts — 60 to 120ml bags are easier than a single large one, because you can thaw only what you need. A thawed bag can't be re-frozen.
• Leave a bit of headroom in the bag or bottle; milk expands as it freezes.

Thawing frozen breast milk

Start for Life says the best way to thaw frozen breast milk is "leaving it in the fridge to thaw out completely before use". That's slow — plan a day ahead if you can. If you can't, the NHS allows two faster methods:

• Stand the bag or bottle in a jug of warm water, or
• Hold it under running warm water.

Two rules the NHS is firm on:

• Never thaw frozen breast milk in a microwave. The NHS says it "can create hot spots in the milk that can burn your baby's mouth" (and microwaves also damage some of what makes breast milk breast milk).
• Never re-freeze defrosted milk. Once it's thawed, it goes in the fridge or in the baby.

Thawed milk in the fridge should be used within 24 hours — or follow the direction from the NHS Start for Life storing-breast-milk page about leftover milk after feeding, which says to throw any away "after feeding".

Warming expressed milk

If your baby prefers warm milk, the NHS says: "You can warm the milk to body temperature by putting the bottle in a jug of warm water or holding it under running warm water." Don't use a microwave or the stove. Shake or swirl the bottle to even the temperature, and test a drop on the inside of your wrist before feeding — body temperature feels neither warm nor cool.

Can I give my baby cold breast milk?

Yes. The NHS puts it plainly: "You can feed expressed milk straight from the fridge if your baby is happy to drink it cold." Some babies take cold milk without a fuss; others prefer it warmed. It's a baby-preference thing, not a safety thing — fridge-temperature milk is fine.

After a feed starts

Once your baby has drunk from the bottle, the clock resets. The NHS says any milk left in the bottle after a feed should be used within 1 hour, and that leftover milk after a feed should be thrown away. In practice, that means offering a smaller amount first (you can always warm a top-up), rather than filling a full bottle and tipping half of it down the sink.

Cool bags and travelling with expressed milk

A cool bag with ice packs holds already-chilled milk for up to 24 hours (the NHS page says this plainly). That covers a day out, a childminder drop-off, a train journey or a hospital stay. Two practical notes:

• Pop the cool bag into a fridge at the other end as soon as you can.
• If the cool bag has been opened often, treat the 24-hour figure as a ceiling, not a floor — use the milk sooner if you can.

Room temperature: the quiet bit

Neither of the two NHS pages linked above gives a specific room-temperature number for freshly expressed milk. If you can, chill the milk promptly — into the fridge as soon as possible after expressing. The UK's Baby Friendly Initiative and some NHS trust leaflets quote longer room-temperature times, but those aren't on nhs.uk, so we don't repeat numbers here. The safe default is "chill it as soon as you can".

A few things to log, so the stash doesn't lose you

• Date expressed (on the bag and in your log). This is the number that decides how long it keeps.
• Volume, so you can match bottles to your baby's current appetite.
• Location — fridge, ice compartment or freezer — because the times are different.
• Anything unusual, like a different taste or smell when thawed. Frozen breast milk sometimes develops a slightly soapy smell from a natural enzyme; many babies take it fine, some don't.

Where CubTrack fits

If you're pumping regularly, the hardest thing isn't the NHS numbers — it's keeping track of which bag was expressed when and whether it's gone past its date. CubTrack's breastfeeding tracker has a pumping log with its own timer and an amount in ml, and a stash view that lists each bag or bottle with fridge-or-freezer tags and the soonest-to-expire first. Your partner sees the same stash on their phone for free, so the person at home with the baby isn't the only one who knows what's in the freezer. It runs on the free tier.

Related reading

• Breastfeeding a newborn (UK guide)
• Combination feeding: a UK guide
• How much milk should a baby drink?
• How long does made-up formula last?
• Cluster feeding explained

Frequently asked questions

How long can breast milk stay in the fridge?

The NHS says up to 8 days at the back of a fridge at 4°C or colder, or within 3 days if you're not sure how cold your fridge is.

How long does breast milk last in the freezer?

Up to 6 months at -18°C or colder (NHS). In the ice compartment of a fridge — the small freezer bit inside — up to 2 weeks.

Can I give my baby cold breast milk straight from the fridge?

Yes. The NHS says: "You can feed expressed milk straight from the fridge if your baby is happy to drink it cold." Some babies prefer it warmed; either is safe.

How do I warm expressed breast milk?

The NHS says put the bottle in a jug of warm water or hold it under running warm water. Never use a microwave or the stove. Test the temperature on the inside of your wrist before feeding.

Can I re-freeze thawed breast milk?

No. The NHS is clear: "Never re-freeze defrosted milk." Once thawed, keep it in the fridge and use within 24 hours.

How long can breast milk sit out at room temperature?

nhs.uk doesn't publish a specific room-temperature figure on its two main storage pages. The safe default is to chill fresh milk promptly — into the fridge as soon as you can after expressing.

How long is milk good for in a cool bag?

Up to 24 hours (NHS), as long as the milk went into the cool bag already chilled from the fridge and there are ice packs in with it. Transfer to a fridge at the other end.

What do I do with the milk left in the bottle after a feed?

Use it within 1 hour of the feed starting, or throw it away. The NHS says leftover milk after a feed should be thrown away.

Storage, warming and thawing information quoted from the NHS in November 2026. This is general information, not medical advice; your midwife or health visitor is the person to speak to about expressing and feeding in your particular situation. CubTrack is made by OakFox Limited.