The shelf life of tea is a common topic of discussion among tea drinkers. We often see questions such as:

• Do tea leaves go bad?
• How long do tea leaves stay fresh?
• Which teas have longer or shorter shelf lives?
• Do tea bags go bad? 
• What happens if I drink old tea?

The short answer is properly stored tea may lose flavor and complexity over time, but generally does not go bad to the point it will be harmful to drink. Also, different types of tea have different shelf lives. 

However, there's a lot more to it, read on for the full scoop...

First, let's look at some of the factors that affect how long your tea stays fresh.

Solar withering is the first stage of oolong tea processing. How long tea stays fresh depends on how dry it is.

Dryness

How long tea stays fresh primarily depends on how well it is dried when it's initially processed. The more moisture remaining in the tea leaves, the more volatile they are and the sooner they will lose their freshness.

The only way any tea leaves will actually spoil is when they are kept in an extremely humid environment, where they will eventually absorb enough moisture to go moldy, so proper storage of tea leaves is important to keeping your tea fresh.

Processing

As a rule, the more processed the leaves are, the easier it is to dry them and stabilize their constitution. Given this, more processed teas will typically have a longer shelf life. So, in general, a green tea will not stay fresh as long as a black tea.

Oxidation

Oxidation can be seen as a method of "curing" the tea leaves to result in various flavor profiles, but it also stabilizes the constitution of the leaves— making them less volatile. There is a broad spectrum of tea types made from partially oxidized tea leaves that include White Tea, Yellow Tea, and Oolong Tea.

Roasting

Any type of tea can be roasted, But for the most part, only sufficiently oxidized Oolong Teas undergo any significant degree of roasting. In addition to oxidation, roasting further cures the leaves, depleting them of any remaining moisture, and making them more stable in their constitution. It also enhances the flavor profile to give it a more full-bodied, bolder character.

Given the above factors, we can make a general list of tea types according to shelf life from longest to shortest.

Shelf Life of Tea Types (Longest to Shortest)

1. Black Tea
2. Heaviliy oxidized, and/or roasted teas
3. Medium oxidized, roasted teas
4. Lightly oxidized unroasted teas
5. Green Tea

Green Tea is made from tea leaves that are dehydrated without undergoing any oxidation, and almost all Green Tea types are unroasted. This makes it the freshest, and consequently the most volatile of all tea types. Black Tea is fully oxidized, which puts it at the opposite end of the oxidation spectrum from Green Tea. In short, the more processed the leaves are, via oxidation and/or roasting, the more stable and less volatile the tea will be — giving the tea a longer shelf life. 

Aged tea?

Conversely, there is the art of aging tea to increase its quality and value. This idea alone may appear to contradict everything we are talking about here, but in fact it still follows the basic drying rule of thumb. Aging tea is actually a form of post production processing to transform the tea's original character of tea into something, well — beyond.

Oolong Tea being aged in ceramic urns, along with some Pu Er cakes simply wrapped in paper on the shelf below.

Aged Tea still needs to be stored in a cool, dry place, without exposure to light. The only thing it's allowed to be exposed to is air — in order to allow a very long slow form of oxidation to occur in the dried leaves that transforms the compounds in the leaves and results in a mellowed, rich character of tea. But aging tea is in a category of its own, and like we said — beyond the scope of this post!

Do Tea Bags Go Bad?

As the tea commonly found in tea bags is a form of loose leaf tea (often ground, lower quality tea as compared to premium loose leaf tea), the rules for storage and shelf life detailed above will apply to most store bought tea bags. However as tea bags may be harder to keep vacuum sealed, they may loose freshness at a faster rate. To be sure, you may also refer to your tea bag packaging for the manufacturer best before date. 

Does Brewed Tea Go Bad? 

Brewed tea will slowly lose its complexity of flavor if left at room temperature for more than a few hours. The tea will eventually sour if left for more that 12 hours. It varies a lot among tea types, some will be fine for at 24 hours. But we recommend not going beyond 6 hours for best results, and no more than 10 hours to be on the safe side. If brewed tea is refrigerated within an hour of being brewed, it should keep for at least 24 hours. 

Pro tip: it's best to remove the leaves from the brewed tea. If brewing "grandpa style" in a single mug and you want to keep the tea for later, pour it off into a second cup. Don't keep leaves in brewed tea for more than two hours! 

LEARN MORE

Now that you know a bit about how long tea stays fresh, check out our post on how oolong tea is made or look at the various ways you can brew oolong tea.

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