Why does tea taste bitter in my mouth?

December 18, 2025 •

4 min read

Over 80% of tea drinkers report experiencing an unpleasantly bitter cup at some point, and it's usually not the tea's fault. To understand why does tea taste bitter in my mouth, one must examine the variables in the brewing process that cause the over-extraction of bitter compounds like tannins and catechins.

Quick Summary

This guide explains the primary reasons behind bitter-tasting tea, focusing on brewing time, water temperature, tea quality, and proper storage. It details how to correct common mistakes to ensure a delicious, well-balanced cup every time.

Key Points

Control Water Temperature: Using water that is too hot, especially for delicate teas like green and white, causes bitterness by over-extracting tannins and catechins.
Mind the Steep Time: Oversteeping is a primary cause of bitterness, as leaving tea leaves in water for too long releases an excess of harsh, bitter compounds.
Choose Quality Tea: Lower-quality tea bags, which often contain broken leaves and dust, have a larger surface area that leads to a faster and more intense release of bitter flavors.
Check Your Water: Water quality and mineral content can affect the taste of your tea; fresh, filtered water is often recommended for the best flavor.
Store Tea Properly: Improper storage exposes tea to air and moisture, dulling its flavor and potentially contributing to unwanted bitterness.
Consider Cold Brewing: For a naturally sweeter, less bitter tea, cold brewing is an effective method that slowly extracts flavor compounds without releasing excess tannins.

The Chemical Culprits: Tannins and Catechins

At the heart of tea's bitterness are natural plant compounds known as polyphenols, specifically tannins and catechins. These are beneficial antioxidants, but when they are over-extracted from the tea leaves, they release an overly bitter, astringent flavor.

Catechins: More prevalent in less oxidized teas like green and white tea, catechins can produce a grassy, bitter flavor if brewed incorrectly. Japanese green teas, like Gyokuro, have a delicate flavor profile that is easily overwhelmed by high temperatures.
Tannins: Black teas, which are more oxidized, contain more tannins and less catechins compared to green tea. When balanced, tannins add desirable depth and body, but in excess, they create a drying, mouth-puckering sensation.

Common Brewing Mistakes That Cause Bitterness

Your brewing method has the single biggest impact on the final taste of your tea. Even high-quality tea leaves can be ruined by improper technique.

Oversteeping

One of the most common reasons for a bitter cup is leaving the tea leaves or bag in the water for too long. As tea steeps, different compounds are extracted at different rates. The flavorful, aromatic compounds come out first, followed by the more bitter-tasting ones like tannins. Leaving the leaves in for too long floods the water with these bitter agents, drowning out the more pleasant flavors.

Incorrect Water Temperature

Different types of tea require different brewing temperatures to release their optimal flavor profile. Using water that is too hot is a frequent cause of bitterness, especially with more delicate teas.

Delicate Teas (Green & White): Need cooler water, typically between 70-80°C (158-176°F). Boiling water can scorch these delicate leaves, releasing too many catechins and overpowering the subtle notes.
Robust Teas (Black): Can handle higher temperatures, closer to boiling at 90-100°C (194-212°F). However, oversteeping even black tea with boiling water can still lead to an excessively bitter cup.

Low-Quality or Old Tea

Not all tea is created equal. Many conventional tea bags contain broken leaves, fannings, and dust rather than whole leaves. This increased surface area causes a rapid, often imbalanced, extraction of compounds, leading to a quick and harsh bitterness. Poorly stored or old tea can also lose its delicate flavors and take on an unpleasant bitter quality. For the best flavor, use high-quality loose-leaf tea and store it in an airtight, dark container.

Poor Water Quality

The mineral content of your water can also affect your tea's flavor. Hard water, which is high in minerals like calcium and magnesium, can interfere with the extraction of tea compounds and result in a cloudy or dull-tasting brew. While some studies show that tap water can provide better flavor than purified water for certain teas, using filtered or fresh water is often the safest bet for a clean taste.

Comparison Table: How Brewing Conditions Affect Flavor


Condition	Effect on Flavor	Best For	What to Avoid
High Temperature	Extracts robust flavors, but can cause bitterness and astringency.	Strong black teas, herbal infusions.	Green and white teas.
Low Temperature	Slow, gentle extraction, highlighting sweetness and umami.	Delicate green and white teas, cold brew.	Black teas (can result in weak, flat flavor).
Long Steep Time	Increases strength, but also maximizes bitter tannins.	Very strong black teas, or if you prefer a bold flavor.	All teas, especially green, if you want to avoid bitterness.
Short Steep Time	Reduces bitterness and highlights subtle, complex flavors.	Delicate teas, multiple infusions.	Can result in a weak, under-extracted brew if too short.

How to Avoid or Fix Bitter Tea

If you've already brewed a bitter cup, you don't necessarily have to throw it out. Here are a few tricks:

Add Milk or Cream: For black tea, a splash of milk can bind with the tannins, neutralizing the bitterness.
Add Sweetener: A little honey or sugar can help balance out and mask the bitter flavor.
Dilute It: Add a little more hot water to your cup to dilute the concentration of bitter compounds.
Cold Brew: For naturally less bitter tea, cold brewing extracts flavor compounds slowly, resulting in a much smoother, sweeter brew.
Check Your Water: If you suspect your water quality is the problem, try brewing with fresh, filtered water.

Conclusion: Mastering the Art of Tea Brewing

Understanding why your tea tastes bitter is the first step toward brewing the perfect cup. By paying attention to the fundamentals—water temperature, steeping time, and tea quality—you can control the extraction of flavor compounds and avoid the pitfalls of excessive bitterness. Remember that brewing is a personal journey of taste, and what works for one tea might not work for another. Experiment with different parameters to find your ideal balance of flavor, and you'll be well on your way to becoming a tea connoisseur.

For more expert advice on tea preparation, see this comprehensive guide: T2 Tea Brewing Guide.

Frequently Asked Questions

The main reason tea tastes bitter is the over-extraction of polyphenols, particularly tannins and catechins, from the tea leaves. This happens most commonly due to using water that is too hot or steeping the tea for too long.

Yes, green tea often becomes bitter more easily than black tea because it contains higher levels of catechins, which are very sensitive to high temperatures. Brewing green tea with boiling water is a common mistake that causes bitterness.

You can fix a bitter cup of tea by diluting it with more hot water, adding a sweetener like honey or sugar to mask the bitterness, or adding a splash of milk or cream to black tea to neutralize some of the tannins.

The correct water temperature varies by tea type. For delicate green and white teas, use 70-80°C (158-176°F). For robust black teas and herbal teas, 90-100°C (194-212°F) is appropriate. Oolongs fall somewhere in between, around 85-95°C.

Using high-quality, whole loose-leaf tea helps prevent bitterness because the leaves extract more slowly and evenly than the dust and fannings found in many tea bags. This allows for more control over the flavor extraction.

Yes, the quality of your water can affect your tea's flavor. High mineral content in hard water can influence extraction, while fresh, filtered water provides a cleaner taste that lets the tea's true flavor shine through.

Drinking bitter tea is generally not unhealthy, as the bitterness comes from natural compounds like tannins and catechins that are beneficial antioxidants. However, excessive tannin consumption can sometimes cause nausea, especially on an empty stomach.