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How To Tell If Oat Milk Is Bad and How Long Does It Really Last?

You opened oat milk that’s past its date, and it seems perfectly alright. That makes you think: how to tell if oat milk is bad?

Or maybe your opened oat milk sits in the fridge for a few days already, and you’re wondering how long does open oat milk last.

If you’re new to oat milk and need a quick primer, you’re in the right place. In this article, we’ll cover:

  • storing oat milk (and why some brands are in the refrigerated section, and others are not)
  • oat milk shelf life – both for an unopened carton and the leftovers
  • telling if your oat milk is still okay to drink or not

Sounds interesting? Let’s dig in.

Oat milk carton
Oat milk carton

How To Store Oat Milk

There are two varieties of oat milk: shelf-stable and refrigerated. Unopened shelf-stable oat milk can sit in your pantry or on a countertop. After opening, store it in the fridge. Refrigerated, as the name suggests, requires refrigeration at all times.

The easiest way to go about it is to store your unopened oat milk the same way they stored it in the supermarket or grocery store.

If it sat on a shelf, it’s the stable shelf variety. If it was in the refrigerated section, perhaps near dairy products such as milk or buttermilk, it’s definitely the variety that requires refrigeration.

Some brands, e.g., Oatly ([OTLY]), sell both oat milk varieties. Don’t assume yours is one type or the other just based on the brand name. Instead, remember where you picked it up, and check the label to make sure.

Oat milk and spinach cake
Oat milk and spinach cake

Shelf-stable oat milk doesn’t require much when it comes to storage. A shelf or cabinet in the pantry or kitchen will do. Just make sure it doesn’t sit in a place where temperature frequently changes. You can even keep it in the fridge if you want.

When it comes to the second kind, all it needs is chilly temperatures. While leaving the carton on the door might not be perfect (that’s the place where the temperature fluctuates the most), it’s not a big deal.

Once you open your carton, always keep it sealed and refrigerated, just like you do with other non-dairy milks such as almond milk, coconut milk, or soy milk.

The difference between shelf-stable and refrigerated oat milk is (usually) packaging ([OTLY]). The former is packaged in an aseptic format that results in a sterile environment inside the carton. That means there are no unwanted microorganisms, meaning there’s nothing to spoil the product (before you open it up). Hence its much longer shelf life.

Oat milk in a glass
Oat milk in a glass

How Long Does Oat Milk Last?

Unopened shelf-stable oat milk lasts for at least a few months past its date, while refrigerated oat milk keeps only for up to a few days past the date on the label. Both retain quality for about 4 to 7 days of opening.

The best-by dates on shelf-stable oat milk are usually between 9 months to a year from the production date. The same period for the refrigerated variety is only a couple of weeks long.

As you can tell, the shelf-stable oat milk lasts way longer than its chilled counterpart.

Date on oat milk carton
Date on oat milk carton

How Long Does Oat Milk Last After Opening?

The popular recommendation for leftover oat milk is to finish it within 4 to 7 days ([TTS]). It’s a decent rule of thumb, but it’s always best to consult the label.

You see, even though oat milk is basically strained blended oats with water, different companies include various extra ingredients. Sometimes it’s a bit of oil to make the liquid smoother or a sprinkle of a sweetener to enhance the taste.

Those slight differences in ingredients and processing may affect the shelf life, especially when it comes to oat milk that’s already open.

Because of that, some brands urge you to finish their product within 4 days, while others give you more slack and say that theirs is fine for up to 10 days of opening.

To experience the best quality, go with the recommendation on the label. The oat milk should be okay (but maybe not great) to drink for another day or two.

Oat milk
Oat milk

Can You Drink Expired Oat Milk?

If it’s the shelf-stable variety and you opened it recently, chances are it’s just fine. Unless, of course, it “expired” a couple of years ago. If that’s the case, the quality might not be that great.

But if we’re talking about the chilled kind and its date was like two weeks ago, it’s better to err on the side of caution and discard it.

What if your oat milk sits in the fridge for longer than the suggested period? Let’s talk about that.

Pouring oat milk
Pouring oat milk

How To Tell If Oat Milk Have Gone Bad?

Start by pouring your oat milk into a glass. Then, discard oat milk if:

  • The texture isn’t smooth. If your oat milk is lumpy, thick (difficult to pour), or slimy, throw it out.
  • Color has changed. Oat milk is creamy white (see my photos). If yours isn’t, most likely something bad happened. Unless, of course, it’s a flavored one, and that color is normal.
  • It smells off. It’s not common for non-dairy milk alternatives to smell sour or bad, but if that happens, that’s a clear sign of spoilage.
  • It sits open for more than 5 days longer than the recommendation on the label. If the label says you should finish the carton within 4 days of opening, and yours is open for 10, it’s time to let it go.
  • There’s mold in the carton. While highly unlikely, I recommend cutting open any old carton to make sure there isn’t any mold inside. You can always transfer leftovers into an airtight container.
Spinach cake and a glass of oat milk
Spinach cake and a glass of oat milk

Assuming none of the above is true, it’s time to give your oat milk a taste.

If it’s okay, which is the most likely outcome, feel free to finish it. If it’s not, or you’re not certain it’s safe to drink, throw it out.

The quality of oat milk gradually decreases after your first open the carton. Therefore, you might notice that the oat milk you opened 4 days ago isn’t as good as it was fresh. If the flavor difference is huge, however, you should get rid of the drink.


  • Store shelf-stable oat milk in the pantry, and transfer it into the fridge upon opening. Refrigerated oat milk should sit in the fridge at all times.
  • Shelf-stable oat milk keeps for at least a few months past its date, while chilled cartons last for only a couple of days past their date.
  • Finish oat milk leftovers within 4 to 7 days.
  • Throw out oat milk that’s lumpy or slimy, discolored, smells bad, or sits for too long in storage.