How Long Does Kefir Last and How To Tell If It’s Bad?

You’ve bought a few bottles of milk kefir to give it a try. The taste was a-okay, but it didn’t rock your world.

Now you have the last bottle sitting in the fridge, and it’s nearing the date on the label. Does kefir go bad?

Kefir is basically fermented milk, similar to sauerkraut which is fermented cabbage or kombucha (fermented tea). That might make you think that since it’s already “spoiled,” there’s nothing bad that can happen to it. Unfortunately, that’s not true.

In this article, we will go through storage, shelf life, and going bad of store-bought milk kefir. We will also touch upon homemade kefir too but won’t go into details of making it.


If you’re interested in making your own kefir, many companies sell kefir starter packs and kefir grains. You can easily choose one and buy the ingredients you need and get started.

Kefir carton in hand
Kefir carton in hand

How to Store Kefir?

Like almost all dairy products, you should store kefir in the refrigerator.

Once you open the bottle or container, make sure you always keep it sealed tightly and refrigerated when not in use. If you won’t finish the bottle or container in one sitting, pour yourself a glass and put the rest back into the fridge.

If you leave kefir at room temperature, it’s going to become super sour and harsh in taste quickly. Plus it’s not a good idea to store kefir on the counter in the first place.


For kefir to retain freshness for longest, place it in the far corner of the fridge instead of on the door. That’s because the temperature in there stays more or less the same, while it fluctuates near the door.

Kefir leftovers ready for storage
Kefir leftovers ready for storage

If your kefir isn’t resealable, here are a couple of ways you can store the leftovers:

Can You Freeze Kefir?

In case you wondered about freezing kefir, you can do it, but many producers advise against it. It’s like yogurt or buttermilk: the liquids separate from solids after freezing and thawing.

While you can blend the thawed kefir, its texture won’t exactly be creamy and delightful as it was before. In other words, you can not turn back time.


Thawed kefir works only in dishes where its consistency doesn’t matter that much, e.g., in cooked dishes or smoothies.

When it comes to how to freeze kefir, I recommend freezing it using an ice cube tray. This way you can easily thaw as much as you need without thawing all of it. If the cubes are too small, feel free to use a muffin tin instead.

When it comes to thawing, put the cubes in the fridge the night before you need them.

Want to learn more about the topic? Check out our article on freezing kefir.

Glass of kefir
Glass of kefir

Freezing kefir and active cultures

Many people who consider freezing kefir worry about the active cultures in the dairy product being killed by freezing.

On some websites, you can find people saying that the cultures go dormant and get active again after thawing. Others state that most of them die.

Right now the best answer to this question seems to be: we don’t know. I haven’t found any credible research on this topic, and I’m not really sure if anyone capable of doing such a test is interested in performing it.


If you’re drinking kefir for the probiotics and good bacteria, don’t freeze the kefir.

Kefir carton
Kefir carton

How Long Does Kefir Last

Kefir stays good for up to a week past its date. Opening the container doesn’t change much in that matter. Its taste becomes stronger over time, and when its around a week past that date, it will often be too strong to drink.

Homemade kefir should last for about 2 to 3 weeks if stored properly. For more specific guidelines consult the instructions given in the kefir starter or on the website of the producer of the grains.

That’s the short version, let’s talk about the details.

Like other dairy products, kefir comes with a date on the package. Most often it’s a sell-by date, but sometimes it literally says “expiration date”. If it’s a sell-by date, you can assume that the kefir should stay fresh for maybe a week more if unopened.


If the label says “expiration,” you can add a few days to that date too. It’s not like the manufacturer tampered with the product for it to go bad the day after the date on the label.

Kefir in a container
Kefir in a container

When it comes to how long does the kefir stay fresh after opening, it depends.

If you open it soon after buying, it pretty much should last until the date on the label. If, on the other hand, you open it near the date on the label, you shouldn’t expect it to stay tasty for more than 5 days.

Obviously, if you open it a couple of days past the date on the label, it’s best if you use it within 24 hours.

Kefir (unopened)Sell-by + 1 week
Kefir (opened)Sell-by or 3 – 5 days if it’s “expired”
Homemade kefir2 -3 weeks

Please note that the periods above are estimates and for the best flavor.

Does Kefir Go Bad? How to Tell If Kefir Has Gone Bad?

Kefir goes bad just as other dairy products do.

To tell if your kefir is bad, look for the following signs of spoilage:

  • Mold or any other fuzzy growth on the surface.
  • Changed color.
  • Off or really sour vinegar-like smell.
  • Heavy separation, like a layer of liquid on top.
  • The product being chunky and difficult to pour, even after shaking the bottle.

If everything seems to be okay, and you don’t already store the kefir for too long, give it a taste.

Assuming that it tastes okay, feel free to drink it or use it in any other way. If it tastes super sour or just not as good as it should, discard it.


It makes no sense to force yourself to drink something you find unappealing. If your kefir seems okay-ish, but you find its taste way too sour, get rid of it.

Kefir closeup on lumps
Kefir closeup, notice the lumps and uneven texture, which are normal

Fresh store-bought milk kefir usually has a pretty uniform and creamy texture. Its flavor depends on the variety. Plain kefir tastes sweetish-tart, but many brands offer flavored kefir, and each one has its unique taste.

That being said, kefir is a live product, so the taste, texture, and level of fizz vary from bottle to bottle.

Those slight variations are natural and by no means mean the product is bad. That’s just the nature of the beast, especially for preservatives-free kefir.

If you find that a certain bottle seems a bit more tart than what you’re used to, that doesn’t mean it’s spoiled. The same is true for thickness, as it also varies a bit from batch to batch and season to season.


If you need kefir for a recipe and yours has gone bad, you can substitute buttermilk for kefir.

FAQs about Kefir

Is kefir supposed to be sour?

Yes, kefir typically tastes like a yogurt-like drink that’s a bit sourer and usually has a somewhat sour smell. Plus, there might be some fizz present, especially when you first open it.
Because of that, you can substitute buttermilk, yogurt, or even half and half with kefir without noticing much of a difference.

Does kefir taste like buttermilk?

Yes, kefir tastes like thin yogurt or buttermilk. The main difference is that your kefir might be a bit effervescent (fizzy, like champagne or carbonated water), and the other two aren’t. Not every milk kefir is fizzy, though, so don’t panic if yours tastes “flat.”

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