What are the side effects of drinking unsweet tea? Exploring the downsides of overconsumption

November 7, 2025 •

3 min read

According to Healthline, while moderate tea consumption is healthy for most people, exceeding 3 to 4 cups per day could have several negative consequences. Knowing what are the side effects of drinking unsweet tea can help you enjoy this beverage responsibly and avoid issues related to its caffeine and tannin content.

Quick Summary

Excessive unsweetened tea intake can lead to caffeine-related symptoms like anxiety, headaches, and poor sleep, as well as digestive problems due to tannins. Overconsumption may also affect iron absorption and contribute to stained teeth.

Key Points

Caffeine Overload: Excessive unsweetened tea consumption can lead to anxiety, headaches, restlessness, and poor sleep due to its caffeine content.
Tannins Irritate the Stomach: The tannins in tea can cause nausea, heartburn, and an upset stomach, particularly if you drink it in large quantities on an empty stomach.
Inhibited Iron Absorption: Tea tannins can bind to and reduce the absorption of non-heme iron from plant-based foods, which is a concern for people with low iron levels.
Dental Staining: Regular and frequent consumption of unsweetened tea can cause discoloration or staining on your teeth due to its tannin content.
Kidney Stone Risk: Although rare, massive black tea consumption has been linked to kidney problems due to high oxalate levels, which can contribute to kidney stone formation.
Caffeine Dependence: Consistent, high intake of unsweet tea can lead to caffeine dependence, with withdrawal symptoms like headaches and fatigue if you stop abruptly.
Individual Sensitivity Varies: The amount of unsweetened tea that causes side effects differs from person to person based on caffeine sensitivity and overall health.

Navigating the Caffeine Conundrum in Unsweet Tea

Even without added sugar, many types of tea contain caffeine, a natural stimulant. While moderate consumption can provide an energy boost, excessive intake, especially for those sensitive to caffeine, can lead to several unpleasant side effects.

Caffeine's Impact on the Body

Exceeding recommended daily caffeine limits can disrupt various bodily functions. An 8-ounce cup of black or green tea typically contains between 15 and 60 mg of caffeine. The FDA suggests a maximum of 400 mg daily for most healthy adults, but individual tolerance varies. High intake can cause:

Increased anxiety and restlessness: Caffeine's stimulating nature can worsen feelings of stress and nervousness.
Sleep disturbances: It can interfere with melatonin, the sleep hormone, potentially leading to insomnia or poor sleep quality.
Increased heart rate: High consumption can accelerate heart rate, a concern for those with heart conditions.
Headaches and dizziness: While caffeine can sometimes alleviate headaches, overconsumption or withdrawal can trigger them, and large amounts may cause light-headedness.

The Role of Tannins and Mineral Absorption

Unsweetened tea contains tannins, plant compounds that give tea its dry, slightly bitter taste. These tannins have some antioxidant properties but can also cause digestive issues and affect nutrient absorption.

Tannins and Digestive Health

Drinking excessive or strong unsweetened tea, particularly on an empty stomach, can lead to gastrointestinal discomfort. Tannins' astringent properties can irritate the digestive tract, potentially causing:

Nausea and upset stomach: Sensitive individuals might experience these symptoms even with a small amount of strong tea.
Heartburn and acid reflux: Caffeine and tannins can increase stomach acid, potentially aggravating acid reflux symptoms.
Reduced iron absorption: Tannins can bind to non-heme iron from plant foods, reducing the body's ability to absorb it. This is relevant for those with anemia or who follow vegetarian/vegan diets.

Comparison of Unsweetened Tea Consumption Risks


Potential Side Effect	Primary Cause	Who is at Risk?	How to Mitigate Risk
Anxiety/Jitters	Excessive Caffeine Intake	Individuals sensitive to stimulants	Monitor daily caffeine intake, switch to lower-caffeine teas or decaf/herbal options.
Nausea	Tannins on an Empty Stomach	Individuals with sensitive digestive systems	Drink tea with food or add milk to help tannins bind to proteins.
Poor Iron Absorption	Tannin Content	Individuals with iron deficiency, vegetarians, vegans	Drink tea between meals, not with them, to avoid hindering absorption.
Stained Teeth	Tannin Content	Anyone who drinks tea regularly	Maintain good oral hygiene, brush or rinse mouth after drinking.
Insomnia	Excessive Caffeine Intake	Individuals sensitive to stimulants or who drink tea close to bedtime	Avoid caffeinated tea in the evenings or switch to herbal tea.
Heartburn	Caffeine and Tannins	Individuals with sensitive stomachs or acid reflux	Reduce intake, avoid strong teas on an empty stomach.

Other Considerations and Health Impacts

Excessive tea consumption can also present other concerns. High levels of oxalates in some teas could contribute to kidney stone formation in susceptible individuals, although this requires very large quantities. Additionally, some teas may contain higher levels of fluoride absorbed from the soil, and excessive intake could lead to health issues related to fluoride overexposure.

In conclusion, unsweetened tea is generally a healthy beverage, but overconsumption can lead to potential drawbacks. Moderation is key, along with understanding your personal sensitivity to caffeine and tannins. By being mindful of your intake and adjusting based on your health, you can enjoy unsweet tea without adverse effects. Always consult a healthcare professional for specific health concerns. Check out Healthline for more detailed information on the side effects of drinking too much tea.

Frequently Asked Questions

For most healthy people, drinking 3 to 4 cups of unsweetened tea daily is considered a safe range. Exceeding this amount can increase the risk of side effects, especially if you are sensitive to caffeine or have underlying health conditions.

Yes, excessive caffeine from unsweet tea can increase feelings of anxiety, stress, and restlessness, especially in individuals who are sensitive to its stimulating effects.

Yes, unsweetened tea contains tannins that can inhibit the absorption of non-heme iron from plant-based foods. To mitigate this, avoid drinking tea with meals and opt to have it between meals instead.

The tannins in tea can irritate the lining of the stomach, which is more likely to cause nausea or an upset stomach when consumed on an empty stomach. Eating food with your tea can help minimize this effect.

Yes, the tannins in tea can cause staining and discoloration of teeth over time with regular and frequent consumption. Practicing good oral hygiene, like brushing or rinsing your mouth after drinking, can help.

No, the side effects can vary depending on the type of tea. For example, black tea typically has more caffeine and tannins than green or white tea, meaning it may have a higher potential for side effects with excessive consumption.

To reduce potential side effects, moderate your intake to a healthy level (around 3-4 cups daily), avoid drinking strong tea on an empty stomach, and consider switching to caffeine-free herbal teas if you are sensitive to caffeine.