Although moderate tea consumption is typically healthy for most people, drinking too much may lead to side effects, such as anxiety, low quality sleep, and headaches. Most side effects are related to tea’s caffeine and tannin contents.

Tea is one of the world’s most beloved beverages.

The most popular varieties are green, black, and oolong — all of which are made from the leaves of the Camellia sinensis plant.

Though moderate tea consumption can be a healthy choice for most people, excessive consumption could lead to some adverse side effects.

Here are 8 possible side effects of drinking large amounts of tea.

Tea is a rich source of a class of compounds called tannins. Tannins can bind to iron in certain foods, rendering it unavailable for absorption in your digestive tract.

Iron deficiency is the most common nutrient deficiency in the world, and if you have low iron levels, excessive tea intake may worsen your condition.

Tannins are more likely to hinder the absorption of iron from plant sources than from animal-based foods. Thus, if you follow a strict vegan or vegetarian diet, you may want to pay extra close attention to how much tea you consume.

The exact amount of tannins in tea can vary considerably depending on the type and how you prepare it.

If you have low iron but still enjoy drinking tea, consider having it between meals as an extra precaution. Doing so will make it less likely to affect your body’s ability to absorb iron from your food at mealtimes.

Some tea leaves naturally contain caffeine, like black and green tea. Overconsuming caffeine from tea, or any other source, may contribute to feelings of anxiety, stress, and restlessness.

Research suggests that an association between anxiety and caffeine may be more pronounced when caffeine doses exceed 400 milligrams (mg). Still, some people are more sensitive to the effects of caffeine than others and may need to limit their intake further.

If you notice your tea habit is making you feel jittery or nervous, it could be a sign you have had too much and may want to cut back to reduce symptoms.

You may also consider opting for caffeine-free herbal teas. Herbal teas are not derived from the Camellia sinensis plant. Instead, they’re made from a variety of ingredients, such as flowers, herbs, and fruit, which are typically caffeine-free.

Because some tea naturally contains caffeine, excessive intake may disrupt your sleep cycle.

Melatonin is a hormone that signals your brain that it’s time to sleep. Some research suggests that caffeine may inhibit melatonin production, resulting in low quality sleep.

Not getting enough sleep can lead to fatigue, impaired memory, and reduced attention span. What’s more, research associates chronic sleep deprivation with an increased risk of obesity and inadequate blood sugar management.

People metabolize caffeine at different rates, and it’s difficult to predict exactly how it affects sleep patterns in everyone.

A 2024 study suggests 100 mg of caffeine within four hours of going to sleep may have minimal to no effect on sleep. However, 400 mg of caffeine within 12 hours of going to sleep may have adverse effects.

The effects of caffeine on sleep may also increase if people consume it closer to bedtime.

If you’re experiencing symptoms related to low quality sleep and regularly drinking caffeinated tea, you may want to consider reducing your intake or switching to decaffeinated or herbal tea.

Certain compounds in tea may cause nausea, especially if you consume them in large quantities or on an empty stomach.

Tannins in tea leaves are responsible for the bitter, dry taste of tea. The astringent nature of tannins can also potentially lead to uncomfortable symptoms, such as nausea or stomachache. The amount of tea required to have this effect can vary from person to person.

If you notice any of these symptoms after drinking tea, you may want to consider reducing the total amount you drink.

You can also try adding a splash of milk or having some food with your tea. Tannins can bind to proteins and carbs in food, which may minimize digestive irritation.

Some research suggests that tea may increase your risk of gastroesophageal reflux disease (GERD), which can cause symptoms like heartburn and acid reflux.

Caffeine may also contribute to an increase in total stomach acid production.

Of course, drinking tea may not necessarily cause heartburn. People respond very differently to exposure to the same foods.

That said, if you routinely consume large quantities of tea and frequently experience heartburn, it may be worthwhile to reduce your intake and see whether your symptoms improve.

Exposure to high levels of caffeine from beverages like tea during pregnancy may increase your risk of complications, such as miscarriage and low infant birth weight.

Data on the dangers of caffeine during pregnancy is mixed, and it’s still unclear exactly how much is safe. However, the American College of Obstetricians and Gynecologists (ACOG) recommends limiting daily intake to 200 mg.

Some people prefer to drink caffeine-free herbal teas in place of regular tea to avoid caffeine exposure during pregnancy. However, not all herbal teas are safe to use during pregnancy.

If you’re pregnant and concerned about your caffeine or herbal tea intake, be sure to seek guidance from your healthcare professional.

Older research from 1997 suggests that large doses of caffeine, typically greater than 500 mg, could lead to dizziness or lightheadedness. If people are sensitive to caffeine, they could experience this symptom from smaller amounts.

Dizziness may also occur as a withdrawal symptom if someone has caffeine dependence and suddenly limits the amount they consume.

If you notice that you often feel dizzy after drinking tea, you may want to consider opting for lower caffeine versions or consulting your healthcare professional.

Caffeine is a habit-forming stimulant, and regular intake from tea or any other source could lead to dependence.

Symptoms of caffeine withdrawal may include:

  • headache
  • irritability
  • increased heart rate
  • fatigue
  • drowsiness
  • mood changes
  • difficulty concentrating
  • flu-like symptoms, such as nausea and muscle pain

The level of exposure required to develop dependence can vary significantly depending on the person. Still, some research suggests it could start after as few as 3 days of consecutive intake, with increased severity over time.

Tea is one of the most popular beverages in the world. It’s not only delicious but also linked to numerous health benefits, including reduced inflammation and a lower risk of chronic disease.

Though moderate intake is healthy for most people, drinking too much could lead to negative side effects, such as anxiety, headaches, digestive issues, and disrupted sleep patterns.

If you’re experiencing any side effects that you think could be related to your tea intake, try gradually cutting back until you find the level that is right for you. If you’re unsure how much tea you should be drinking, consult your healthcare professional.