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How long can oat milk be left out and still drinkable?

Oat milk has become an increasingly popular plant-based milk alternative in recent years. Made from soaked oats and water, it has a creamy, nutty flavor that many people enjoy. But there are some important food safety considerations when storing oat milk, especially regarding how long it can sit out unrefrigerated before spoiling.

What is Oat Milk?

Oat milk is a vegan milk alternative made by soaking oats in water, then blending the mixture and straining out the oat pulp. The strained liquid resulting liquid resembles the consistency of dairy milk. Oat milk has a mildly sweet, oaty flavor that makes it suitable for drinking, pouring on cereal, using in coffee drinks, and more.

The main ingredients in oat milk are:

  • Oats
  • Water
  • Salt (optional)
  • Natural sweetener like sugar or maple syrup (optional)

Some brands may also add sunflower or canola oil for a richer consistency and vitamins and minerals for nutritional fortification.

Is Oat Milk Dairy Milk?

No, oat milk is not dairy milk. True dairy milk comes from cow, goat or sheep mammary glands. Oat milk contains no dairy ingredients whatsoever. This makes it suitable for vegans and people with dairy allergies or intolerances.

How Long Does Oat Milk Last When Unopened?

Unopened, commercially packaged oat milk generally stays fresh for 5-10 days past the printed expiration date when stored in the fridge. For optimal quality, try to consume refrigerated oat milk within a week of opening. Here are some general oat milk shelf life guidelines for unopened cartons:

Oat Milk Type Refrigerator Freezer
Shelf-stable, unopened 4-6 months past printed date 1 year
Refrigerated, unopened 7-10 days past date 3-4 months
Homemade 3-4 days 1-2 months

How to Tell if Opened Oat Milk Has Gone Bad

Once opened and exposed to air, oat milk has a shorter shelf life. Here are some signs that opened oat milk has spoiled and should be discarded:

  • Sour smell & taste: Fresh oat milk should smell sweet and nutty. If it smells sour or bitter, it has likely spoiled.
  • Chunky texture: Spoiled oat milk may become grainy or chunky in texture rather than smooth.
  • Mold growth: Check the oat milk for fuzzy mold spots, which indicate it is inedible.
  • Expired date: If the oat milk is past its expiration date, err on the safe side and throw it away.

How Long Does Opened Oat Milk Last in the Fridge?

Once opened, oat milk stored in the refrigerator generally stays fresh for:

  • Cartons: 7-10 days
  • Jugs: 5-7 days
  • Homemade: 3-4 days

The shorter shelf life for jugs is because the larger container size means it takes longer to use up, allowing more time for the oat milk to deteriorate. Homemade oat milk has the shortest fridge life since it lacks the preservatives found in store-bought brands.

Does Oat Milk Go Bad?

Yes, oat milk can go bad once it surpasses its expiration date or refrigerated shelf life. Being plant-based, oat milk still contains sugars, proteins and water molecules that allow bacteria and mold to grow over time, causing spoilage.

The main reasons oat milk goes bad are:

  • Bacterial growth – bacteria feed on sugars and proteins.
  • Mold – fuzzy mold spores thrive in damp environments like refrigerators.
  • Oxidation – fats react with oxygen and go rancid.
  • Yeast production – yeasts ferment natural sugars.

Bad oat milk will have an off taste and appearance. Don’t take risks by consuming oat milk past its prime.

How Long Can Oat Milk Sit Out?

Oat Milk Type Room Temperature Cooler w/ Ice Packs (≤40°F)
Shelf-stable, unopened 3-5 days 7-10 days
Refrigerated, unopened 2-3 days 5-7 days
Refrigerated, opened 4-6 hours 1-2 days
Homemade 2-4 hours 1 day

As a general rule of thumb:

  • Unopened, shelf-stable oat milk can be left out at room temperature for 3-5 days before consumption.
  • Once opened, oat milk should not sit out for more than 4-6 hours before being refrigerated.
  • A cooler with ice packs extends the fridge life by a day or two.

How to Store Oat Milk Correctly

To get the longest shelf life out of oat milk once opened, follow these storage guidelines:

  • Refrigerate after opening – Keep oat milk chilled at 40°F or below.
  • Store in the back – Place cartons towards the back of fridge shelves where temps are coldest.
  • Check for expiry dates – Don’t consume oat milk past the “best by” or expiration date.
  • Keep lid tight – Screw lids on tightly to prevent fridge odors from tainting milk.
  • Use clean utensils – When pouring, use clean spoons and glasses.
  • Finish within 7-10 days – Consume opened cartons within a week and a half.

Can You Freeze Oat Milk?

Yes, you can safely freeze oat milk to extend its shelf life. Freeze it in airtight containers leaving some headspace to allow for expansion. Thaw frozen oat milk overnight in the fridge before using. The consistency may be slightly thinner after thawing but it is still perfectly drinkable.

Here are some freezing guidelines based on oat milk type:

Oat Milk Type Freezer Life
Unopened, shelf-stable carton 1 year
Unopened, refrigerated carton 3-4 months
Opened carton 1-2 months
Homemade 1-2 months

Is it Safe to Drink Oat Milk After it Expires?

It’s generally not recommended to consume oat milk past its printed expiration date. However, some people may wonder if oat milk is still safe to drink a certain amount of time after expiring. Here are some general guidelines on consuming expired oat milk:

  • Unopened, shelf-stable oat milk: Often still safe up to 5-7 days past printed date if refrigerated after opening.
  • Unopened, refrigerated oat milk: Risk consuming 2-3 days past date, but expect poorer flavor/texture.
  • Opened oat milk: Not recommended to drink more than 1-2 days past expiration.
  • Homemade oat milk: Discard 1 day past expiration for optimal safety and quality.

Keep in mind oat milk could still spoil before the printed date if stored improperly. Always do sensory tests like smelling before consuming expired oat milk.

Common Questions about Oat Milk Freshness

Does oat milk need to be refrigerated?

Before opening, shelf-stable oat milk can be stored at room temperature. But refrigeration extends the shelf life. Once opened, oat milk must be refrigerated and consumed within 7-10 days.

Can you microwave spoiled oat milk?

No, microwaving will not make spoiled oat milk safe to drink. The bacteria and mold toxins remain even after heating. Always discard oat milk once it spoils.

Is it safe to drink oat milk after freezing?

Yes, properly frozen and thawed oat milk is 100% safe to consume. The freezing process halts bacteria and mold growth. Thaw frozen oat milk overnight in the fridge before using.

Can curdled oat milk make you sick?

Yes, curdled or lumpy oat milk may harbour harmful bacteria and should not be consumed. The change in texture indicates the proteins and fats have degraded. When in doubt, throw it out.

Does oat milk need refrigeration after opening?

Absolutely. To prevent rapid spoilage, opened oat milk must be stored in the fridge. Drink refrigerated oat milk within 7-10 days and don’t leave it sitting out for more than an hour.

Key Takeaways on Oat Milk Freshness

  • Unopened, shelf-stable oat milk stays fresh about 5-10 days past its printed expiration date.
  • Once opened, oat milk lasts 7-10 days in the fridge.
  • Don’t drink oat milk that smells sour, tastes funky, or has mold spots.
  • Discard opened oat milk cartons after a week in the fridge.
  • Oat milk can be frozen for 1-2 months to extend its shelf life.
  • Drink refrigerated oat milk within a week and homemade oat milk within 3-4 days.
  • Don’t consume oat milk more than 1-2 days past its expiration date.

Understanding how long oat milk stays fresh can help prevent foodborne illness. Follow safe storage times, check for signs of spoilage, and freeze excess oat milk to maximize its shelf life.


Oat milk is a tasty, non-dairy milk substitute, but it does have limited refrigerator and counter life once opened. To ensure safety and quality, store unopened oat milk in the fridge and consume opened cartons within 7-10 days. Discard oat milk that smells or tastes foul, or has passed its printed expiration date. Freezing can significantly prolong the shelf life of oat milk. Being mindful of proper storage methods and freshness times will keep oat milk safe and prevent bacterial or mold growth.