How long does milk last once opened?

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How long does milk last once opened? The definitive guide
The nation’s big question, answered. We break down exactly how long milk should last, what shortens its life, and how to keep it fresh for longer
Fridge temperatures and date labels make the difference to your milk (
Image: Getty Images)
By
Ginette Davies Senior Commercial Writer
09:00, 2 Mar 2026
Updated 10:05, 5 May 2026
We all know that you shouldn’t cry over spilt milk, but what about spoiled milk? Because let’s be honest, reaching into the fridge only to find that your milk has gone off is enough to send even the most pragmatic of adults into a toddler-like tantrum.
While milk is something that most Brits use every day, few of us understand what’s actually going on inside the bottle.
But with just a little knowledge – and a few simple switches – your milk could stay fresh for days or even weeks longer.
Intrigued? Then read on for your definitive guide.
The real reason why milk goes off
Follow this guide to get the best out of your milk, whatever the bottle
(
Image:
Getty Images)
The first thing you need to know is that milk doesn’t go off because it’s old, but because the bacteria in the milk have multiplied.
When this happens, the lactose (milk sugar) is converted into lactic acid, which gives the milk a sour taste and causes the proteins to clump, resulting in a thick, lumpy texture.
Although there is nothing you can do to stop your milk from eventually going off, there are a number of ways you can slow the process down.
The first is to make sure you don’t introduce any new bacteria into the milk, which is why drinking straight from the bottle is an absolute no-no.
The second is to keep your milk perfectly chilled, as bacteria multiply much faster above 4°C.
How long should your milk last?
The shelf life of your milk will depend on two things: the type of milk you buy, and how you look after it.
Nowadays, “milk” comes in all shapes and sizes – traditional cow's milk, ultra-filtered, UHT, and an ever-increasing variety of non-dairy options. But what do all of these terms mean, and do any of them guarantee your milk will stay fresh for longer?
Pasteurised cow's milk
From pasture to fridge: what’s the true shelf life of your milk?
(
Image:
Arla Cravendale)
The vast majority of the milk sold in the UK is this. Pasteurised milk has been heated to a temperature of around 72°C for at least 15 seconds before being rapidly cooled back down to 4-5°C. Pasteurisation removes harmful bacteria and pathogens (such as salmonella, listeria and E. coli), and has the added benefit of extending the shelf life of the milk, so that it stays fresh for up to 10 days unopened and three to seven days once opened.
Non-dairy “milks”
From nut milks to varieties made from grains and legumes, there is now a plethora of plant-based milk alternatives on the market. Of these, oat milk is by far the most popular and, like cow's milk, it comes in both refrigerated and UHT form.
Refrigerated oat milk lasts for around 7-14 days unopened, and about five to seven days once opened. UHT oat milk lasts months unopened, but once opened it must be refrigerated and used within 7-10 days.
Filtered milk
Arla Cravendale packages its filtered milk in non-tranparent bottles to protect it from light to help it last longer
(
Image:
Arla Cravendale)
If you’ve seen filtered milk in your supermarket and wondered what sets it apart from standard pasteurised milk, here’s the lowdown. Filtered milk is pasteurised cow's milk that has been through extra filtration to further reduce the number of microbes and bacterial spores.
As a result, fresh filtered or ultra-filtered milk like Arla Cravendale lasts for an impressive seven days after opening and 21 days unopened – substantially longer than standard pasteurised options
UHT milk
Of all the milks on the market, UHT (ultra high temperature) milk has the longest shelf life – although unlike pasteurised or filtered cow’s milk, and refrigerated non-dairy milks, UHT milk is not “fresh”.
This is because it is heated to a temperature of around 140°C for just a few seconds. This kills virtually all microorganisms and spores in the milk, as well as giving it its distinctive sweet, or “cooked”, taste. When properly packaged in an aseptic container, UHT milk can last for six to nine months in a cool, dark place, and around seven until 10 days once opened.
Best practice fridge storage
As temperature is key to maintaining the freshness of your milk, how you store it in your fridge can make all the difference.
The first thing you need to do is make sure your fridge is the right temperature. To keep those bacteria in check, you ideally want it around 2-3°C
The second thing to consider is where in the fridge you store your milk. Contrary to convention, the handy shelf on your fridge door is the worst possible place, as it’s one of the warmest spots. Instead, if possible, you should store your milk near the back, where it’s cooler.
How filtered milk extends freshness naturally
From farm to fridge, discover the Arla Cravendale difference
(
Image:
Richard Walker)
As mentioned, of all the fresh milk options, filtered milk lasts the longest. This isn’t because anything has been added to the milk, but what has been taken away.
At Arla Cravendale, once milk is collected, it’s taken to specialised dairies, where it’s put through five ceramic filters, that remove the impurities, while still keeping all the good stuff in.
As a final step, Arla Cravendale packages its filtered milk in opaque bottles to protect it from light, which again can make it spoil faster.
So that’s the secret to why filtered milk stays fresher for longer: a few further steps and some extra care.
Quick checklist: is it still good?
All supermarket milk will have a “use by” or “best before” date, but these are only estimates. In some cases, your milk will go off before the date on the bottle. Other times, it could last a lot longer.
Here’s a simple checklist to help you determine whether your milk is still fresh:
Smell it: fresh milk smells neutral or slightly sweet. If it smells sharp, sour or “cheesy”, it is on the turn.
Look at it: if your milk looks lumpy, stringy or unusually thick, it’s past its best.
Try the hot water test: add a small splash of milk to a mug of hot (not boiling) water. If it immediately curdles or splits, the milk is on the turn. If it blends smoothly, it’s probably still fine.
Taste it: if your milk passes the first three tests, it is more than likely to be OK, despite what the “use by” or “best before” date might say. If you want to confirm this, it’s time for a taste test. Pour a small amount of milk into a glass and take a tiny sip. Sourness means it’s time to pour it away.
Visit arlafoods.co.uk/brands/arla-cravendale to discover more.
This article was written by Siam Goorwich
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