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Can Kefir Go Bad?

Most of us would be better off if we consumed more probiotics. And that’s probably why you decided to try drinking kefir in the first place, right?

This dairy drink is most known for containing lots of healthy bacteria, and the health benefits they provide.

But as a fermented product, it’s not always clear how to tell if kefir is spoiled or not, or how long you can keep it in storage.

That’s where this article comes in. In it, we go through all the storage-related information regarding kefir. We’ll talk about spoiled kefir and how to tell if yours is okay or not, its shelf life, and how you should go about storing it.

If you’re new to kefir and would like to learn a bit more than what’s on the label of a kefir bottle, this article is for you.

Please note that I won’t be covering making homemade kefir, as there are dozens of great resources on this topic on the Internet. Besides, most people coming here have bought kefir in the supermarket, and aren’t interested in making it on their own.

With that in mind, let’s start by talking about kefir going bad.

Kefir carton
Kefir carton

Can Kefir Go Bad? How To Tell If Kefir Is Bad?

When it comes to signs that your kefir has gone bad, look for the following:

  • Presence of mold on top of kefir. That’s the most obvious sign ([YK]). It might be a noticeable fuzzy growth, or just a few pink or orange spots here and there.
  • Heavy separation. If it looks more like water and a bunch of almost solid chunks, it’s not good anymore. It should be similar to buttermilk in texture.
  • Off or too sour smell. Sure, kefir often smells a bit sour or vinegar-like, but if it was mild after opening the carton and now it’s harsh and biting, get rid of it.
  • Tastes too sour. As a living product, kefir becomes stronger in taste and potency over time ([CG]). And at a certain point, you will find it’s too much for your taste buds. If that’s the case, discard it or perhaps try using it in a recipe where that flavor will fit right in.

Overly sour kefir is perfectly safe to consume, maybe just not the most taste-buds-friendly.

Cooked kefir-based pancakes
Cooked kefir-based pancakes

I want to reiterate that kefir is a fermented milk drink ([WIKI]), and as such, it has all the characteristics of other fermented products, like sauerkraut or kombucha.

The taste, texture, and the amount of fizz in kefir will be different from batch to batch, and they also change depending on the season ([LW]).

The fact that this bottle doesn’t taste or feel exactly like the other bottle from the same producer doesn’t mean it’s spoiled. Kefir is an alive and active product, and every bottle or carton is somewhat unique.

Preparing for kefir pancakes
Preparing for kefir pancakes

How Long Does Kefir Last?

Like with all fermented foods, this one is tricky.

One way to go about it is to assume that it doesn’t go off ([CG]), and throw it out once the taste is too strong, or it actually spoils. But it’s okay if you’re not super comfortable with that approach, as it’s not the only option available.

You can also go about it the more traditional way by observing the date printed on the label. Since kefir is a fermented food, treat that date as an indicator of how long the taste of the dairy drink should be optimal.

Kefir should retain quality for around two to three weeks or until the date on the label. Once the product passes that date, sooner or later its taste will become too strong. It usually takes between five days to a week, depending on your taste preferences.

Kefir pancakes up close
Kefir pancakes up close

Please note that that period will vary from batch to batch, and from person to person. Some people will find it sour much quicker than others.

If the kefir is “expired,” make sure you check for all described signs of spoilage before consuming it.

Once you open the package, the shelf life doesn’t really change ([LW]), but there’s always a chance of microbial contamination causing the kefir to spoil. That means it’s not a given that the kefir you’ve opened 2 weeks before its date will last up to that date in top-notch quality.

Like with similar dairy products such as buttermilk or sour cream, it’s best to consume this fermented milk drink as soon as possible.

Measuring kefir for pancakes
Measuring kefir for pancakes

How To Store Kefir?

You should keep kefir in the fridge, plain and simple.

Refrigeration keeps it safe for consumption, but also prevents the fermentation from accelerating. And that quite a long shelf life I talked about is due to the fermentation going slowly and steadily.

Once you open the container, make sure the leftovers are sealed tightly.

If the kefir comes in a bottle or a resealable carton, that’s not an issue. But if it comes in a non-resealable plastic container, it’s probably best to pour the leftovers to a mason jar, especially if you expect to keep them around for a few days.

Aluminum or plastic wrap and a rubber band is a decent makeshift solution if you don’t have any containers around.

But what if you’d like to keep kefir for longer? While it has a quite long shelf life, if you have much more on hand than you need, you could use an extra couple of weeks of storage time, right?

Pancake batter prep
Pancake batter prep

Can You Freeze Kefir?

Freezing kefir, same as freezing yogurt, is somewhat tricky.

If you freeze the whole container, the solids separate from the liquid after thawing. Stirring and running it through a blender helps, but doesn’t fully reconstitute it.

To reduce this effect, try freezing it using an ice cube tray ([LW]). Pour the liquid into the tray, freeze the cubes, and transfer them to a freezer bag once rock solid. You will probably need to blend it after thawing either way, but the effects should be better.

Pancakes and kefir in background
Pancakes and kefir carton in background

Nevertheless, some of kefir’s creamy consistency will be lost in the process ([LW]). That means you probably won’t enjoy drinking that kefir on its own. But using it for a smoothie, or in a cooked recipe should work just fine.

The loss of creaminess won’t be as noticeable in such a dish, as other flavors will take over, and everything should blend together just fine.

In some recipes the frozen and thawed kefir might not work as well as in others. It’s best to run a test before making a big batch.

When it comes to the question of whether or not the probiotics survive the freezing, it’s difficult to tell. Chances are some of them will become dormant when frozen and active again once thawed, but I didn’t find any legitimate research or tests on this subject.

In other words, if what you care about the most when drinking kefir is your health, do your best to drink it fresh.


  • Kefir is a living product and varies in taste, consistency, and the amount of fizz in every bottle. Slightly different flavor or mouthfeel doesn’t mean it’s spoiled.
  • If there’s mold on the surface, the dairy product smells terrible or has completely separated, throw it out. If it’s super sour, it’s safe for consumption, but feel free to discard it if it’s too much for your palate.
  • Keep kefir refrigerated, and always appropriately sealed.
  • Frozen and thawed kefir works well in smoothies and cooked dishes but not doesn’t taste that well on its own. Freeze in an ice cube tray and stir or blend after thawing.