How long does breast milk last? Fridge, freezer and thawing times

How long breast milk lasts depends on the temperature, whether it's fresh or has been thawed, and which country's guidance you follow. In Australia, the Australian Breastfeeding Association's storage table, which it adapted from Australia's National Health and Medical Research Council Infant Feeding Guidelines (2012), gives freshly expressed milk 6 to 8 hours at 26°C or lower and 72 hours at the back of the fridge. The CDC's storage guide gives 4 hours at room temperature and 4 days in the fridge, and the NHS guide to expressing and storing breast milk gives up to 8 days in a fridge at 4°C or lower.

Three rules are shared by all of them: label milk with the date you expressed it, never refreeze milk that has thawed, and throw away milk left over after a feed. This guide sets out each country's numbers side by side, then covers thawing, warming, leftovers, transport, power cuts and milk that smells a little odd. For how much milk to store, see building a milk stash.

How long does freshly expressed breast milk last?

These times are for milk you've just expressed into a clean container. They don't apply to milk that has been frozen and thawed, warmed, or already offered to your baby; those have shorter limits, set out further down.

A few details sit behind those numbers:

• Australia. The Australian table says to use a fridge rather than room temperature if one is available, and to store milk at the back of the fridge where it's coldest. Its 6 to 12 month figure is for a chest or upright manual-defrost deep freezer that is opened infrequently and holds its temperature.
• UK. The NHS says that if you're not sure of your fridge's temperature, or it runs between 5°C and 10°C, use the milk within 3 days.
• US. The CDC says about 6 months in the freezer is best and up to 12 months is acceptable. It also says not to store milk in the fridge or freezer door.

Why do breast milk fridge times differ so much?

The fridge row is where guidance differs most: 72 hours in Australia, 4 days in the US and up to 8 days on the NHS storage page. The NHS's own breastfeeding and going back to work page gives a shorter figure, up to 5 days at 4°C or lower. Both NHS pages drop to 3 days if your fridge is warmer than 4°C or you aren't sure.

Each table also assumes a different fridge temperature: 5°C or lower for the Australian figure, 4°C or lower for the NHS figures. A family fridge that is opened often or packed full may not stay that cold, and the NHS back-to-work page suggests buying a fridge thermometer so you can check.

The practical rule:

1. Follow one set of guidance, usually your own health service's, rather than picking the longest number from each chart.
2. Use the shorter time if you aren't sure how cold your fridge is or how long the milk has been out.
3. Freeze early. If you won't use milk within your fridge limit, freeze it soon after expressing rather than near the end of that limit.

How long does thawed breast milk last?

Once frozen milk has thawed, the clock is much shorter, and it depends on how the milk was thawed.

The CDC counts its 24 hours from when the milk is completely thawed, not from when you took it out of the freezer. The Australian Breastfeeding Association also says not to reheat breast milk more than once.

The easiest way to use these rules is to move the next day's portions from the freezer to the fridge the night before. Milk that thaws slowly in the fridge has the longest window under Australian and US guidance.

What should I do with breast milk left over after a feed?

Once your baby has started drinking from a bottle, the leftover milk has a short life and can't go back into storage:

• Australia: the Australian table keeps it only for the rest of that feed, then it's thrown away. In the fridge, it's discarded.
• UK: the NHS says that once your baby has drunk from a bottle of breast milk, it should be used within 1 hour and anything left over thrown away.
• US: the CDC says to use the leftover milk within 2 hours, then discard it.

To waste less, the Australian Breastfeeding Association suggests offering small amounts and adding more if your baby is still hungry. Paced bottle feeding also helps your baby take what they need rather than what's in the bottle.

How do I store expressed breast milk safely, step by step?

1. Wash your hands. The CDC says to wash your hands well before expressing or handling breast milk, or use a hand sanitiser with at least 60% alcohol if soap and water aren't available.
2. Use clean, sterilised equipment. The NHS says to make sure the pump and container are clean and sterilised before you use them. Cleaning steps are in pumping basics.
3. Choose a suitable container. The Australian Breastfeeding Association lists food-grade, BPA-free bottles, containers with tight-fitting lids, zip-lock bags, and syringes for colostrum. The CDC says never to use disposable bottle liners or plastic bags not made for breast milk.
4. Store small portions. The NHS says small quantities help avoid waste, and the CDC suggests 60 to 120 mL (2 to 4 oz) or the amount your baby takes at one feed.
5. Leave room to expand. Fill containers no more than three-quarters full (Australian Breastfeeding Association), or leave about 2.5 cm (1 inch) at the top (CDC).
6. Label every container with the date you expressed it. For childcare, the CDC says to add your child's name.
7. Store it at the back of the fridge or freezer, away from the door.
8. Use the oldest milk first. The CDC calls this "first in, first out".

Can you combine milk from different sessions?

Yes. The Australian Breastfeeding Association says to cool freshly expressed milk in the fridge first, then add it to chilled or frozen milk and put the container back. Because the container now holds milk from more than one session, go by the date of the oldest milk when you work out how long it keeps.

How do I thaw and warm breast milk?

1. Thaw slowly if you can. The NHS says it's best to defrost frozen milk in the fridge, and the CDC suggests the fridge overnight.
2. Thaw faster in warm water. If you need it now, stand the sealed container in a jug of warm water or hold it under warm running water (NHS, CDC).
3. Never use a microwave or the stove. The NHS warns this can cause hot spots that burn your baby's mouth.
4. Mix the fat back in. Fat separates in stored milk. The CDC suggests swirling it, and the NHS suggests a gentle shake.
5. Warm only if your baby wants it. The CDC says breast milk doesn't need to be warmed, and the NHS says you can give it cold if your baby accepts it. If you warm it, aim for body temperature and test a few drops on your wrist.

Don't refreeze thawed milk, and don't reheat milk a second time.

How do I transport breast milk or cope with a power cut?

For travel or the trip home from work, the CDC says milk can stay in an insulated cooler with frozen ice packs for up to 24 hours, and the NHS says milk that's been cooled in the fridge can be carried in a cool bag with ice packs for up to 24 hours. When you arrive, use it, refrigerate it or freeze it straight away. The Australian Breastfeeding Association says special measures may not be needed in cool weather or on short trips, but to use an insulated bag on warm days or longer trips. Workday logistics are covered in returning to work.

If frozen milk thaws on the way, the Australian Breastfeeding Association says to use it within 24 hours and not refreeze it.

For a power cut, the Australian Breastfeeding Association suggests:

• Keep the freezer closed. Frozen milk may stay frozen for up to 48 hours, depending on how full and how big the freezer is.
• Move milk if you can to a working freezer, or an insulated cooler with ice packs or other frozen items.
• Prepare if an outage is likely by keeping milk in the centre of the freezer and filling empty spaces, for example with containers of water.
• Check what's thawed. Milk that is partly thawed and still has ice crystals can be refrozen; fully thawed milk should be thrown away.

Is breast milk that smells soapy or looks different safe?

Usually, yes. The Australian Breastfeeding Association's guide to unusual colours and smells says stored milk can smell soapy or "off" because of oxidation after lipase, a fat-digesting enzyme in milk, has done its normal work. It says the milk is still safe and most babies won't notice. Milk can also pick up smells from the fridge or its container.

If your baby refuses milk that smells soapy, the association describes scalding freshly expressed milk before storing it: heat it until just below boiling (not in a microwave), then cool it quickly in iced water and store as usual. It says to do this only if your baby won't drink the milk, because scalding removes some of the milk's immune benefits.

White lumps or a creamy layer on top are usually fat that has separated and risen. Red or brown milk usually means there's blood in it, often from a cracked nipple, and the association suggests checking with your doctor.

When should I get help?

Those emergency signs come from the NHS guide to spotting a seriously ill baby.

Get medical advice the same day (your GP or a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US)) if your baby is not feeding, keeps vomiting, or seems unwell and you're not sure what to do.

Talk to your GP or child-health nurse, or a breastfeeding helpline (the Australian Breastfeeding Association on 1800 686 268 in Australia, the National Breastfeeding Helpline on 0300 100 0212 in the UK), if your milk is red or brown, your baby regularly refuses stored milk, you're expressing for a baby in hospital, or you'd like help with a storage plan for work or childcare.

If your baby is premature or unwell

Home storage charts are written for healthy babies at home. For a premature or sick baby in hospital, the NHS says to ask the hospital staff caring for your baby how to store your milk. The Australian Breastfeeding Association says to talk to your doctor or midwife about any extra steps if your baby is premature or unwell, and that fresh breast milk each day is best for sick babies.

What's worth writing on the label?

The date and time you expressed the milk are the essentials. If a container is moved to the fridge to thaw, add the time it fully thawed, and note when a bottle was warmed or offered, so whoever gives the next feed knows which time limit applies. If you don't know when something happened, write "unknown" and use the shortest limit, or discard it.