Left Oat Milk Out Overnight – Still Safe to Drink?

You’ve woken up in the middle of the night feeling hungry and a glass of delicious oat milk is just what you need. You pour yourself one but accidentally leave the milk carton out on the kitchen counter and go back to sleep. Is the milk still safe to drink the next day or is it bound for the bin? Let’s find out!

So, is it safe to drink oat milk left out overnight? Sadly, no. If you leave oat milk out on the kitchen counter overnight, your best bet is to throw it away as it becomes a breeding ground for harmful bacteria that can make you very sick upon consumption.

Read on for more information on the shelf life of oat milk, what happens to it at room temperature, how long it lasts, the best way to store it, and much more.

Refrigerated vs. Shelf-Stable Oat Milk

Oat milk is a popular dairy-free alternative that is made by blending oats with water. The mixture is strained to separate the pulp, the result of which is a creamy liquid that resembles cow’s milk.

It is a plant-based milk that is not only vegan but also lactose-free, nut-free, soy-free, and gluten-free. A perfect alternative for people with lactose intolerance, celiac disease, or nut allergies, oat milk is a great source of B vitamins and soluble fibers and tastes great too!

You can buy it anywhere these days and can use it in place of dairy milk for all kinds of dishes and recipes.

Before we move on to the shelf life of oat milk and the best way to store it, you need to understand the difference between the two variants of oat milk available in the market – refrigerated and shelf-stable oat milk.

At the supermarket, if you’ve ever noticed two types of oat milk, one in the cool section of the store and the other in the non-refrigerated aisle, it’s because they are different and have unique characteristics and storage requirements.

1. Refrigerated Oat Milk

Refrigerated oat milk is kept in the refrigerated section of the supermarket and comes in a carton made of cardboard. It needs to be refrigerated at all times, regardless of whether it has been opened or not.

2. Shelf-Stable Oat Milk

This type of oat milk can be found in the non-refrigerated section of the supermarket and comes in Tetra Pak packaging. The special packaging results in a sterile environment that doesn’t allow any unwanted microorganisms to spoil the milk.

It doesn’t require refrigeration unless it is opened, and an unopened pack of shelf-stable oat milk can remain at room temperature for weeks or even months without spoiling.

Oat Milk Out Overnight – Does It Go Bad?

Compared to other non-dairy milk, oat milk has a shorter shelf life even when it is stored properly. That being said, you have to be very careful about how long you leave it out at room temperature.

Since oat milk is a perishable item that must be stored properly, leaving it out overnight, particularly if it is the refrigerated kind or if the carton is opened, renders it unsafe to consume.

According to the USDA, once opened, both refrigerated and shelf-stable oat milk shouldn’t be left out at room temperature for longer than 2 hours.

The reason for this is that bacteria thrive at temperatures ranging between 40°F and 140°F, also known as the “danger zone”, and can pose potential health risks.

In situations where the room temperature exceeds 90°F, the safe time range decreases even further and the food becomes unsafe for consumption after only 1 hour.

What Happens if You Drink Oat Milk Left Out Overnight?

Leaving refrigerated or opened oat milk out overnight causes it to go bad, and drinking spoiled oat milk might result in severe food poisoning symptoms including diarrhea, vomiting, nausea, stomach cramps, and even fever.

These symptoms may often be misinterpreted as that of a common stomach bug, but the severity may vary depending on the type and amount of bacteria present, as well as other factors such as the individual’s health and immune system response.

The symptoms of the common types of food poisoning mostly settle within 8 to 48 hours of exposure and are not usually serious. However, in certain serious cases, you may require the assistance of a medical professional and the right medication to recover from them.

Keeping all of this in mind, experimenting with oat milk, or any other perishable food item that has been left out overnight, is not a good idea. It’s always better to err on the side of caution and throw away oat milk that you suspect has gone bad.

How Long Does Oat Milk Last?

Unopened shelf-stable oat milk can last for an extended period, usually months or even years, compared to refrigerated oat milk which tends to have a much shorter life. 

Make sure to always refer to the “use-by” date indicated on the packaging to know for sure how long the oat milk will maintain its quality.

An unopened carton of shelf-stable oat milk should last between 6 to 12 months before its quality starts to deteriorate. Make sure to store it in a cool and dry place in your kitchen pantry, away from direct heat and sunlight.

As soon as you open the shelf-stable carton of oat milk, it needs to be refrigerated within 1 to 2 hours, and you have between 4 and 7 days to use it before it starts to go bad.

Refrigerated oat milk needs to always be refrigerated and will last only a couple of weeks when unopened. Once opened, like the shelf-stable variety, it must be used within 4 to 7 days.

How to Tell if Oat Milk Has Gone Bad?

Oat milk, both in the refrigerated and shelf-stable variety, has a limited life and will start to go bad after a certain period.

Since it is not advisable to drink oat milk that has gone bad due to improper storage or expiration, you need to be able to tell whether it is safe to consume or should be poured down the drain.

Luckily, there are some very easy ways to tell if your oat milk has gone bad and is past its prime. They include:

1. Storage Conditions

The right storage conditions play an integral part when it comes to the lifespan of edible and perishable products such as oat milk.

If you have refrigerated oat milk and have failed to keep it in the refrigerator, chances are that it has gone bad after an hour or two at room temperature.

Once opened, both refrigerated and shelf-stable oat milk must be kept refrigerated. If not, the same rule applies and they’ve probably gone bad at room temperature.

2. Date of Opening

Every package of oat milk comes with a “use-by” date as well as a disclaimer to use it within a certain number of days after opening.

If your opened carton of oat milk has been lying in the refrigerator for longer than the recommended period, which is usually 4 to 7 days, it is best to proceed with caution.

3. Assess Its Appearance

A simple way to tell if oat milk has gone bad is by assessing its appearance. You can start by checking its packaging. If it seems damaged or broken or has puffed up, there’s probably something wrong.

Shake the carton thoroughly and pour some into a glass. If it looks separated or lumpy or if the color has changed, there’s a good chance that it has gone bad. Oat milk with visible mold should also be discarded immediately.

4. Smell the Milk

Like dairy milk, spoiled oat milk starts to give off a sour, rancid, and off-putting smell that can instantly tell that it has gone bad.

Therefore, to check its quality, give your oat milk a good whiff. If it doesn’t have its usual sweet, nutty smell, it’s time to throw it down the drain.

5. Taste It

This should be the absolute last step and must only be done if your oat milk passes all the above-mentioned tests.

Oat milk has a delightfully sweet and creamy taste that works perfectly as a substitute for dairy milk. Take a small sip of the oat milk and if it tastes like it should, you’re in luck and can safely drink the rest. If it tastes even slightly weird, it’s better to discard it and use a fresh carton.

Related Questions

Now that you know if it is safe to drink oat milk left out overnight, here are a few additional questions we thought you might have:

How Long Does Oat Milk Coffee Last at Room Temperature?

Oat milk coffee shouldn’t be left at room temperature for more than 2 hours. After 2 hours, it becomes susceptible to bacterial growth and unsafe to drink.

Can You Leave Soy Milk Out Overnight?

Like other dairy and non-dairy milk products, leaving soy milk out overnight is not recommended as bacteria and harmful microorganisms can grow in the milk making it unsafe for consumption.