Can Oat Milk Go Bad? Here’s What You Need to Know

Plant-based milks are all the rage right now and oat milk, in particular, has a lot going for it. For starters, this dairy-free milk alternative is an excellent source of B vitamins and soluble fiber—and it’s quite tasty, too. That said, if you’re only using it in small quantities—a splash in your coffee once a day, for example—it might take you some time to finish a carton of the stuff. So, can oat milk go bad? (Spoiler alert: Yes, it can, but read on for the full scoop.)

Yes, both refrigerated and shelf stable oat milk will go bad eventually, although the latter lasts much longer than the former. An unopened container of shelf-stable oat milk will stay fresh for six to 12 months, and at least two months (likely longer) past its date. An unopened carton of refrigerated oat milk, on the other hand, should be discarded if it’s more than a week past the printed use by date. Both types of oat milk should be consumed within 10 days of opening.

According to the USDA, a carton of oat milk can safely sit out for up to two hours. After that, you best toss it out. In other words, if you made yourself a cup of coffee and then let the oat milk linger on the counter while you, say, made yourself an omelet and washed the dishes, then you’re OK to stash it back in the fridge. But if you made yourself a cup of coffee in the morning, left for the office and returned to find your oat milk sitting out at 5 p.m.…not so much. (Psst: The two hour rule applies to all perishable foods left out at room temperature.)

This one is pretty straight forward, but shelf-stable oat milk can be stored in the pantry until it’s opened, at which point it should be tightly sealed and sent straight to the fridge. Refrigerated oat milk should immediately be stored in the same fashion you bought it (i.e., the fridge) and, again, always tightly resealed after opening.

Spoiled oat milk won’t necessarily make you sick, but it absolutely can. According to the USDA, foods that have gone bad due to spoilage bacteria will taste unpleasant but are unlikely to make you sick. That said, spoiled foods that have developed pathogenic bacteria, the kind that multiply like nobody’s business when food is left at room temperature for more than two hours, will give you food poisoning. Since there’s no way to determine what kind of bacteria have caused your oat milk to go south, it’s best just to steer clear of the spoiled stuff entirely.

So your opened carton of oat milk has been languishing in the fridge for slightly over a week but less than ten days, and you’re not sure if you can trust it. No need to stand around giving it the side-eye, friends. Instead follow these steps to determine whether or not the milk has spoiled, so you can proceed with confidence.

Step 1: Determine when you opened the carton. If it has been more than ten days, go ahead and throw it out. If you don’t know, make an educated guess…but going forward, we suggest making a habit of writing the date directly on the carton at the time you open it.

Step 2: Smell the milk. Open the carton and take a big whiff. Oat milk that smells rancid (i.e., sour), moldy or weird in any way should be discarded.

Step 3: Assess its appearance. Thoroughly shake the carton (you should always do this before using oat milk) and pour some in a glass. If it looks strange (i.e., congealed or separated) then there’s a good chance it has spoiled. Needless to say, you should also take a hard pass on oat milk with visible mold.

Step 4: Take a sip. If your oat milk has checked out so far, go on and give it a taste. If your palate tells you that something is off, don’t keep drinking; but if it still has that delightfully sweet and creamy taste, then go ahead and enjoy.