Can Kombucha Go Bad? How to Tell and How Long It Keeps

What normal looks like

Live, unpasteurized kombucha often contains brown stringy bits, cloudy haze and sediment at the bottom of the bottle. These are usually yeast and bacteria, and they are not a sign of spoilage. A thin, pale film or a new baby SCOBY forming on top of a bottle that has sat for a while is also normal for raw kombucha.

Taste and carbonation change too. Over days and weeks, the drink becomes more sour as the culture keeps working and the remaining sugar is consumed. It may also lose sweetness and taste closer to vinegar. A very sour kombucha is not necessarily unsafe, but it may not be pleasant to drink straight.

Signs kombucha has gone bad

The clearest sign is mold. Mold appears as fuzzy, dry, raised patches on the surface, and it may be white, green, blue, gray or black. If you see it on a SCOBY or on the liquid, discard the entire batch. Other warning signs include a rotten, cheesy or solvent-like smell instead of a tart, vinegar-like one, and a slimy texture that is unlike the normal thin film.

Bulging lids and gushing bottles are a pressure issue rather than proof of spoilage, but they deserve care. Open bottles slowly, ideally over a sink and pointed away from your face. Trust your senses and your caution. If anything about the smell or look is truly alarming, pour it out. A small loss is better than the risk of illness.

How long store-bought kombucha lasts

Commercial kombucha usually carries a best-by date printed on the bottle, often several months after bottling, and the manufacturer's date is the best guide for sealed bottles stored as directed. Most brands recommend keeping it refrigerated because cold slows fermentation and reduces the buildup of pressure and sourness.

Once opened, drink it within a few days for the best flavor and fizz, since carbonation fades and the taste changes. Bottles left at room temperature can continue to ferment, become more alcoholic and sour, and build pressure. Check the label for any storage notes specific to the brand, because pasteurized and raw products can behave differently.

How long homemade kombucha lasts

Homemade kombucha has no printed date, so judge by smell, taste and handling. Finished plain kombucha stored in the refrigerator in a sealed bottle generally keeps well for weeks, and many brewers drink it within a month or two for the best flavor. Beyond that it can become very sour but is often still fine for use in dressings or marinades if it smells right.

Flavored second-ferment bottles are more variable, since fruit and juice add sugar and change the microbe balance. Refrigerate these after the carbonation you want has formed and drink them sooner. Labeling bottles with the date they were made and the flavors you used helps you keep track, and our guide to labels for fermentation jars covers some handy options.

See labels for fermentation jars →

Why bottles get fizzy, flat or gushy

Carbonation comes from yeast producing carbon dioxide in a sealed bottle. More sugar, more warmth and more time all raise the pressure. A bottle that stays flat usually has too little sugar left, a weak yeast population or a leaky seal. Neither flat nor fizzy means the drink is spoiled, so use smell, sight and taste to judge safety instead.

If a bottle gushes when opened, chill it well before opening, as cold liquid holds gas better. Release the seal in tiny steps to let pressure out gradually. Next time, shorten the second ferment, use less fruit or juice, or refrigerate sooner. Burping a test bottle each day can show you how fast pressure is building in your own kitchen.

Storing kombucha properly

Keep finished bottles cold and away from heat and sunlight. Use bottles designed for carbonated drinks, such as swing-top bottles or sturdy glass, and avoid filling them to the brim, since some headspace helps manage pressure. Never use thin or cracked glass, and avoid storing sealed bottles somewhere warm where pressure could build.

If you are making a large amount, plan your batches so you are not left with more than you can drink. Our swing-top bottle guide covers options for sealed second fermentation. Bottles that have been open for a long time or that contain obviously changed sediment, color or smell should be checked carefully before drinking.

Compare swing-top bottles →

Who should be extra careful

Because raw kombucha is unpasteurized, some groups are usually advised to be careful, including people who are pregnant, have weakened immune systems or take certain medications. Children are also often advised to avoid homemade versions, partly because of the alcohol and acidity. If this applies to you, talk to a doctor before drinking it.

Homemade kombucha also contains trace alcohol and some caffeine, and the amounts are not measured. If you notice stomach upset or any unusual reaction, stop drinking it and seek advice from a health professional. When making your own, use clean equipment, start with enough acidic starter tea and avoid ceramic with unknown glaze, since acid can leach metals from unsafe glazes.