How long does Kefir last in the fridge once opened?
Turning the range into a date
Kefir keeps 1–2 days in the fridge once opened. Two clocks run on this item: one from the day it went into storage and one from the day the seal broke. Both are listed below, 2 rows in all.
- Unopened · in the fridgeUse by1 week after the day you bought it
- Once opened · in the fridgeUse by1 day to 2 days after the day you opened it
Why the freezer is not an option here
The USDA marks the freezer as not recommended for this item, so the answer comes from the refrigerator after opening figure: 1 day to 2 days. The source fills 2 of its fields outside the freezer here, and every one of them is printed below. It is not a warning: food held at 0 °F stays safe, so a not-recommended is a verdict on what would come out of the freezer.
Every storage figure the USDA publishes for this item
The refrigerator is the only place the USDA gives this item a storage time, as it does for 64 of the 466 foods the USDA lists.
- In the freezernot recommended
- Unopened · in the fridge1 week
- Once opened · in the fridge1 day to 2 days
Can you freeze kefir?
The USDA does not recommend freezing kefir. It is not a safety warning, since food held at 0 °F stays safe, but it comes back changed. Keep the fridge at 40 °F or below and the freezer at 0 °F.
How to tell if kefir has gone bad
Go by the date first: kefir keeps 1–2 days in the fridge once opened. Sour or off smell, lumps in milk or cream, and mold mean it goes out. On hard cheese, cut away 1 inch around a moldy spot; soft cheese with mold goes out whole.
Sources: USDA FSIS: the danger zone USDA FSIS: freezing and food safety USDA FSIS: molds on food FDA: are you storing food safely FoodSafety.gov: the FoodKeeper app.
Is it still safe to eat, or just past its best?
The answer at the top of this page reads 1 day to 2 days in the fridge once opened. What decides that is the food and not the shelf the source files it on: Kefir, fermented milk is an animal food, or made with one. Past it, it is not safe to eat: throw it out without tasting, because bacteria build up while food still looks and smells fine.
It is past the date. Now what?
Say the calculator above puts Kefir, fermented milk past its 1 day to 2 days in the fridge once opened window, or the container sat out on the counter overnight. Throw the container out without tasting it, and count any hours it already spent out of the refrigerator as part of that window rather than on top of it.
The USDA's limit for perishable food standing at room temperature is 2 hours, or 1 hour when the kitchen is above 90 °F, and that clock runs whatever the storage figure says. The whole rule, including the cases the source does not cover, is set out under what to do when the date has passed.
Items that behave the same way
The 6 items below are the closest match to this item by storage behavior, running 4 days to 10 days and bracketing its 1 week.
Where these numbers come from
Every storage time on this page is the USDA’s own published figure from the FoodKeeper data, one of the 9 it keeps per food, reproduced unchanged and never an estimate of ours. Where the USDA lists several kinds under one name, each kind keeps its own windows, and the page names the kind its answer is for. The dates and multipliers are ours, computed from those ranges.
Source: USDA FoodKeeper, retrieved 1 September 2026. Found a figure that does not match the source? Tell us on the contact page. How the site is built is on the method page.
USDA index terms: fermented, fermented milk, Kefir, milk
KeepsUntil is an independent reference built on public USDA data. It is not affiliated with, endorsed by, or connected to the U.S. Department of Agriculture or the Food and Drug Administration. Whether a given window is a safety limit or a quality window is stated on the page that prints it.