by
mohit bohra
| May 12, 2025
Updated on - 27 Jan 2026
Green tea is prepared using the unoxidised leaves of the Camellia sinensis herb. It is one of the least processed tea leaves and contains the highest amount of antioxidants. The beverage is prepared by steeping the leaves in hot water for a few minutes.
Research suggests that this can aid in weight loss. However, excessive long-term consumption of green tea can lead to various health issues due to its caffeine content. Read on to know more about the potential side effects of green tea consumption and what precautions to take to remain safe.
Side effects of green tea
Some of the side effects of green tea are as follows:
1. Caffeine sensitivity and sleep disturbances
For some people, the caffeine quantity in green tea can make it harder to sleep. Even though it is a beverage with less caffeine as compared to coffee and cocoa, it can still cause restlessness and light insomnia if you are sensitive.
Green tea also contains the amino acid L-theanine. Although linked to relaxation, it can sometimes cause alertness and hyperfocus if you consume the drink later in the day. Since it’s mildly diuretic, having it close to bedtime might cause frequent trips to the bathroom. If you’re caffeine-sensitive, it’s best to avoid green tea at least 4 to 6 hours before sleep.
2. Impact on the stomach and digestion
Drinking green tea, especially on an empty stomach, can sometimes do more harm than good. The tannins in it can increase stomach acid and lead to issues such as nausea and discomfort. If you already have acid reflux often, green tea may make the symptoms worse.
The beverage is also reported to have caused constipation for some people, as tannins bind with proteins and slow down digestion.
3. Effects on liver health
High doses of green tea, particularly in supplement or extract form, can strain the liver. Concentrated catechins, especially epigallocatechin gallate (EGCG), have been linked to rare cases of liver injury. This risk is mainly associated with green tea extracts, which contain much higher EGCG levels than brewed tea.
Since supplement quality and concentration can vary, some products may pose additional risk. If you plan to take green tea supplements, consult your doctor and choose trusted brands.
4. Iron absorption and nutrient deficiency risks
Green tea can also interfere with how your body absorbs and uses certain nutrients. The tannins in green tea can bind to iron, reducing its absorption from food. Over time, this may lead to iron deficiency, especially in individuals who already have low iron levels or follow vegetarian diets.
Drinking large quantities of green tea can affect the absorption of folate and other minerals. To minimise this, it’s best to drink green tea between meals rather than alongside food. Pairing it with vitamin C–rich foods like oranges or strawberries can also help improve iron absorption and balance out potential nutrient losses.
5. Risks related to weak bones and seizures
Excessive green tea intake can interfere with calcium absorption, which may contribute to weaker bones over time, especially in people with osteoporosis or low calcium levels.
High caffeine consumption can also overstimulate the nervous system and may increase the risk of seizures in individuals who are already vulnerable.
Those with bone health concerns or a history of seizures should speak to a healthcare professional before consuming green tea regularly, particularly in strong or concentrated forms.
6. Possible interactions with medications
Green tea can interact with several medications, altering how they work or increasing side effects. Here are some important interactions to be aware of:
- Heart medications: High doses of green tea can reduce the effectiveness of beta-blockers and interfere with cholesterol-lowering drugs.
- Blood thinners: Green tea may interact with blood thinners like warfarin, affecting its ability to prevent blood clots.
- Stimulant medicines: Combining green tea with stimulant drugs or nicotine can increase heart rate and blood pressure.
- Liver and nerve drugs: It can slow down how the body processes riluzole and theophylline, potentially increasing their side effects.
- Osteoporosis medication: Green tea may interact with raloxifene, reducing its effectiveness.
If you take any of these medications, it’s best to speak with your doctor before making green tea a regular part of your diet.
Who should avoid or limit green tea?
Green tea is not suitable for everyone. If you are sensitive to caffeine, you may experience jitters and insomnia after having the beverage. People with digestive issues like acid reflux, stomach ulcers or irritable bowel syndrome (IBS) may notice increased discomfort, as green tea can irritate the stomach lining. Individuals with iron deficiency should also be cautious, as compounds in green tea can reduce iron absorption from food.
If you are pregnant or breastfeeding, it is best to limit green tea consumption as excessive caffeine can affect the baby’s development or sleep patterns. People taking prescription medications, particularly blood thinners or heart medicines, should consult a doctor before regular consumption to avoid unwanted interactions.
Safe consumption tips for green tea
Here are some easy-to-follow tips that you can adopt in your daily lifestyle in order to safely consume green tea:
- Limit intake to 3-5 cups per day for most healthy adults.
- Avoid on an empty stomach. Drink between meals to prevent nausea or acidity.
- Enjoy in the morning or early afternoon to avoid sleep issues.
- Allow 30–60 minutes post-meal before drinking to support iron absorption.
- Green tea is mildly diuretic, so balance it with enough plain water.
Brewing tips:
- Brew with hot (not boiling) water, at about 65-80°C.
- Steep for 1-2 minutes to extract flavour without bitterness.
- Avoid reusing bags. Reuse once at most and use fresh leaves for each cup.
- Add lemon or mint for taste; avoid milk as it can reduce antioxidants.
Health precautions:
- Consult your doctor, especially if you’re pregnant, anaemic or on medication.
- Watch caffeine intake. Too much caffeine can cause headaches and irregular heartbeat.
When to seek medical advice
If you experience unusual symptoms like persistent nausea, dizziness or a rapid heartbeat after drinking green tea, it’s best to consult a doctor. These could signal caffeine sensitivity or other underlying issues that need medical attention.
People with liver problems and other chronic conditions, such as hypertension or diabetes, should check with a healthcare professional before making green tea a regular habit. If you take prescribed medicines, ask your doctor about possible interactions to avoid complications.
Having medical insurance can provide additional support, ensuring timely treatment and financial protection if complications arise, such as liver concerns or adverse reactions with medications.
Conclusion
Now that you’ve read about the possible side effects of green tea, it’s clear that even healthy habits need balance. Green tea offers many benefits, but overconsumption or unmonitored use can lead to issues like digestive discomfort or nutrient imbalances. Consuming it in moderation is the simplest way to enjoy its goodness safely.
If you or your loved ones experience health problems from lifestyle changes or dietary choices, having health insurance for family can make a big difference. It ensures everyone in your home has access to quality medical care when needed, without the stress of unexpected costs. You can get tailored health insurance advice by filling out the form on this page.
FAQs
1. Can green tea cause a hormonal imbalance or affect thyroid function
Excessive green tea consumption, especially from concentrated extracts, can interfere with thyroid hormone production. People with hypothyroidism should consult a doctor before making it a daily habit.
2. Is it safe to drink green tea while taking iron or calcium supplements?
Not immediately. Green tea can reduce the absorption of minerals like iron and calcium. It’s best to wait at least one to two hours after taking supplements before having a cup.
3. Does green tea affect blood sugar control for diabetics?
In some cases, yes. Green tea can enhance insulin sensitivity, but when combined with diabetes medication, it might lower blood sugar levels too much. Diabetics should monitor their glucose levels closely and seek medical advice on safe intake.
Disclaimer: The information provided in this blog is for educational and informational purposes only. It is not intended as a substitute for professional advice, diagnosis or treatment. Please consult a certified medical and/or nutrition professional for any questions. Relying on any information provided in this blog is solely at your own risk, and ICICI Lombard is not responsible for any effects or consequences resulting from the use of the information shared.