It is a common belief that green tea is one of the healthiest drinks. Several studies and research talk about its health benefits. Thus, people consume it without any regulation to reap several benefits. However, do we ever stop to think of whether an excess of green tea consumption might have it’s negative effects too? Like any other food and beverage, excess green tea consumption has potential side effects. This article highlights a few of these side effects.

Green tea comes from the leaves and buds of the Camellia sinensis plant. Different varieties of tea belong to the same plant. However, the processing stage differentiates them. Since green tea is one of the least processed types of tea than its other variants, it imparts all the goodness. The preparation of green tea involves unoxidised leaves. Therefore, they contain multiple nutrients which impart health benefits. In addition, green tea contains antioxidants that benefit our health. Anti-oxidants are compounds that prevent oxidative stress to the cells. It, in turn, restricts the radical cell injury. 

Green tea also contains a potent antioxidant called EpiGalloCatechin Gallate (EGCG). It helps combat diseases like Alzheimer’s, arthritis, heart disease, cancer, and obesity. But, an age-old proven theory is that consumption of anything in excess takes away all the benefits and leads to several side effects. The latest research shows that excess consumption of green tea may cause adverse or side effects. It results in multiple health disorders and complications. For example, excess green tea consumption may lead to side effects like anaemia, IBD, liver toxicity, and thyroid issues.

Side Effects of Excess Green Tea

Although green tea imparts various health benefits, excess green tea consumption leads to complications and adverse effects. Therefore, it is essential to consume it in moderation. In addition, some people should avoid green tea consumption. For example, pregnant and lactating mothers should refrain from drinking green tea and products made from its extracts. Furthermore, doctors may advise people with hypertension to avoid green tea under certain medications.

1. Anaemia

Research proves that anaemia results from iron deficiency. Low iron levels in your blood may cause iron deficiency, reducing haemoglobin. Iron is necessary to synthesise haemoglobin because it is the oxygen-carrying pigment in red blood cells. These cells carry oxygen to other body cells.

Green tea contains a pigment named epigallocatechin gallate (EGCG), which binds iron in the blood, reducing iron content. As a result, it prevents iron absorption, leading to iron deficiency and reducing your haemoglobin count. Low haemoglobin levels may result in breathlessness, fatigue, and weakness.

2. Drug Interactions

Caffeine in green tea stimulates your nervous system. The stimulation makes you rejuvenated and fresh. However, caffeine interacts with certain medications. As a result, it leads to adverse effects or complications.

Usually, caffeine breaks down and gets eliminated from your body. However, studies reveal that some medications prevent their breakdown. Instead, they cause the accumulation of caffeine in your body. It elevates the adrenalin levels in your body, which can potentially shoot your blood pressure and heart rate. Such medications include antibiotics, birth control drugs, and anaesthetic drugs.

Caffeine also prevents the action of certain antipsychotic drugs like Clozapine, Metazolam, and Lithium content drugs. As a result, it prevents absorption, resulting in drug accumulation in the blood. As per research, such drug accumulation results in clozapine toxicity and can also cause lithium toxicity.

Vitamin K in green tea also interferes with the effects of Warfarin, an anticoagulant or anti-blood-clotting drug. As a result, it can initiate bleeding in patients with bleeding disorders.

3. Triggers Inflammatory Bowel Diseases (IBD)

You should avoid drinking green tea if you have IBD. That is because the EGCG binds with iron in your body and restricts the inhibition of an enzyme named myeloperoxidase. The enzyme triggers inflammation in inflammatory bowel diseases. As a result, it causes inflammation and other symptoms, including stomach pain and vomiting.

4. Harmful During Pregnancy

During pregnancy, excessive green tea consumption may impact both the mother and the foetus. It causes hypertension in mothers and increases the heart rate. Both the conditions are harmful. Caffeine also increases urination, resulting in loss of your body fluid. It causes dehydration. Blood pressure may exert force on your heart and kidney, resulting in disorders. Blood pressure might also cause contractions in the uterus, resulting in preterm delivery.

Caffeine and tannins in green tea can also lower the folic acid content in your body. Folic acid is vital during pregnancy because it prevents anaemia. Low folic acid leads to low haemoglobin levels. Furthermore, it causes dizziness and breathlessness. In addition, folic acid also prevents any changes in DNA. It protects you from various disorders. For example, it prevents newborn abnormalities like spina bifida, a brain disease. As per studies, spina bifida is a congenital deformity, a condition by birth. Folic acid also prevents the fusion of a newborn’s spinal cord with the backbone.

5. Low Potassium Levels

Potassium is an essential element for multiple functions in your body. For example, potassium impacts nerve function, heart rhythm, and muscle contraction. Unfortunately, excessive caffeine through green tea lowers potassium levels because caffeine has diuretic properties, flushing salt content from your body. As a result, it causes a potassium deficiency, which can prove fatal in many ways. For example, it causes muscles weakness, cramps, altered heartbeat, and even paralysis.

6. Liver Toxicity

Epigallocatechin gallate (EGCG), a pigment in green tea, imparts various health benefits. However, excess concentration makes the liver release enzymes to break down or metabolise caffeine. It exerts a load on the liver and disturbs its smooth functioning. The caffeine content harms the liver cells and results in liver toxicity, which can cause jaundice and urine discolouration. Symptoms of liver toxicity include headache, dizziness, and palpitations.

7. Affects Thyroid Function

A higher concentration of caffeine and catechins impairs thyroid function. It blocks the absorption of thyroid hormones. An imbalance in thyroid hormones may result in nervousness, confusion, and irritability. It also affects the absorption of vitamins, causing many disorders like abnormal weight gain, weight loss, and temperature sensitivity. In addition, excess caffeine and catechins also affect the absorption of essential minerals. Furthermore, an imbalance in thyroid hormones during pregnancy may impact the growth of the foetus.

8. Impacts Bone Strength

Flavonoids are essential for bone growth. However, higher doses impact bone growth and density. In addition, the caffeine in green tea might restrict calcium absorption, which results in low calcium levels in the bone. Calcium is the central element for bone health. Calcium deficiency affects bone growth and strength, increasing the risk of fractures and reducing bone density. Therefore, you should take any tea extract supplements under the supervision of doctors. It will help you avoid the side effects.

Moreover, the excess flavonoids trigger mutations. Mutations are permanent changes in the DNA or RNA, resulting in diseases or disorders. Flavonoids in green tea also release free radicals that induce cell injury. They form the basis of inflammatory and degenerative diseases like arthritis and osteoporosis.

9. Anxiety and Insomnia

Caffeine in green tea is a nervous system stimulant. Optimal doses lower stress levels and induce sleep. However, excess amounts may trigger sleeplessness and anxiety, resulting in restlessness and irritability.

10. Induces Bleeding

Again, caffeine in green tea has anti-clotting properties. Thus, it prevents clotting and initiates profuse bleeding. You will prominently observe this during injury or in surgery. Warfarin is an anticoagulant drug that prevents stroke and cardiac arrest. Caffeine interferes with its effect. In addition, vitamin K in green tea is also an anticoagulant.

11. Causes Heartburn

Heartburn is a common symptom of a gastroesophageal disease (GERD), commonly known as acidity. Green tea contains theophylline that enhances the acidic environment in your stomach. An abnormal acidic environment triggers the food contents to return to the food pipe, resulting in acid reflux or heartburn. As per research, excessive green tea consumption, smoking, and obesity trigger heartburn.

Excess green tea consumption also induces Asymptomatic Erosive Oesophagitis. It is a worsened stage of heartburn. The frequency of this disorder is higher in people who drink green tea frequently.

12. Stomach Disorders

Caffeine also has laxative properties. It is a gastrointestinal stimulant that enhances the food pipe muscle contractions. That means it facilitates bowel movements. However, excess consumption may induce diarrhoea and abdominal pain.

13. Low Blood Pressure

Caffeine has diuretic properties, which makes your body eliminate salt, sodium and water. In addition, caffeine triggers the urinary bladder to induce the frequency of urination. It also drains water from your blood and reduces the fluid level. As a result, it lowers your blood pressure. Therefore, people on diuretic medication should be cautious while taking green tea. It may further lower your blood pressure and result in dizziness, lightheadedness, fainting, vomiting, and weakness.

14. May Cause Infertility in Men

In a 2018 study at the University of California-Irvine, researchers warn that excessive consumption of Green Tea may adversely affect fertility. That is due to the flavonoids in green tea. However, these flavonoids are beneficial to health. But, an excess causes impaired sperm synthesis and sperm motility and decreases testosterone levels. Testosterone is the male reproductive hormone. In addition, caffeine impacts the DNA in sperm, affecting sperm viability and impacting reproduction.

15. Impacts Your Teeth

Regular consumption of green tea might cause stains on your teeth. It is because the tannins in green tea may seep into your teeth cells and impart discolouration or stains. Moreover, the acidic content in coffee might also dissolve the enamel. Therefore, it aggravates tooth discolouration. Staining also causes discolouration of the skin in your mouth.

16. May Cause Headaches

Some individuals might suffer from headaches after consuming green tea. That is because it contains caffeine. An excess of caffeine may trigger headaches. Thus, people with migraine should only have it occasionally. Avoid drinking it daily, especially if you suffer from headaches more frequently. Likewise, you should not consume it if you have a caffeine sensitivity.

17. Vomiting

Excessive green tea consumption may also lead to nausea and vomiting. It is due to the presence of tannins and the way protein binds in your intestines. Thus, the amount of green tea you can drink in a day should be moderate.

Quantity of Green Tea You Should Have Per Day?

Every food or drink has some or other side effects. Green tea is nothing different. Unfortunately, along with the beneficial side of green tea, side effects also persist. However, it happens when you over consume it. So you should consume it in moderation. Anything under two cups per day is safe.

However, drinking more than 3-4 cups of green tea per day may have adverse health effects. 

Another fact is that the side effects are not confined only to the dose. They are also related to allergy or sensitivity. The best solution is to check with your doctors before including it in your regular diet. The quantities may vary according to your body weight, underlying medications, and allergies.


Green tea has multiple health benefits. However, excessive intake might harm you. Although these side effects can result from some allergies, they are almost certain to occur with excess consumption. Therefore, it is essential to limit your green tea consumption to moderate. In addition, most of the side effects of excess green tea consumption are due to caffeine. Hence, it is also essential to regulate your caffeine intake through other beverages and foods.

Lime juice, tulsi tea, ginger tea, and cinnamon tea are excellent substitutes for green tea. Their nutritional composition imparts medicinal properties. As a result, they benefit your health. However, moderate consumption of green tea is safe, and on your doctor’s advice, you can add it to your regular diet and enjoy the health benefits.

Frequently Asked Questions (FAQs)

Q. What happens if you drink too much green tea?

A. While green tea is usually good for health, it can lead to the following side effects if taken in excess:

  • Anaemia
  • Inflammatory Bowel Syndrome
  • Low Potassium Levels
  • Liver Toxicity
  • Affect Thyroid Function
  • Impacts bone strength
  • Anxiety and Insomnia
  • Induces bleeding
  • Stomach disorders

Q. What happens if I drink 10 cups of green tea a day?

A.10 cups of green tea can be considered excess. Therefore it might lead to all such diseases as enlisted above. Further, it may also induce:

  • Low Blood Pressure
  • Heartburn
  • Infertility in Men
  • Headaches
  • Vomiting

Therefore, you must take care to consume green tea in limited amounts. One should not exceed more than 3 cups a day. It is healthy to drink one or two cups of green tea daily.

Q. Does green tea affect periods?

A. No, green tea does not affect your periods. While it is an excellent way to calm raging hormonal changes, it cannot induce or delay periods. However, it helps in boosting blood flow during menstruation and soothes period cramps. 

Q. Who should not drink green tea?

A. Green Tea is usually considered good for health. However, people with a medical history of bleeding should avoid green tea. That is because green tea has a blood-thinning effect. In addition, it contains small amounts of caffeine, which can induce bleeding in the first place. Furthermore, pregnant women should also avoid consuming green tea.

Q. Is drinking too much tea bad for your kidneys?

A. Tea often contains oxalic acid, which causes a culmination of waste in the kidneys. These may, in turn, lead to kidney failure and other kidney-related diseases. In addition, consuming more than 5 cups a day can lead to specific adverse effects on the body and even kidney stones.

Q. Does green tea make you bleed?

A. Yes, the caffeine present in green tea can make you bleed. It prevents clotting and initiates profuse bleeding. You will prominently observe this during injury or in surgery. Warfarin is an anticoagulant drug that prevents stroke and cardiac arrest. Caffeine interferes with its effect.

Q. Is green tea good for skin?

A. Yes, usually green tea is considered suitable for the skin because it contains anti-inflammatory properties that help maintain the sheen of the skin. Moreover, green tea is also the solution to several dermatological conditions. In addition, green tea is rich in significant antioxidants and vitamin C, which provide anti-ageing properties to the skin.

Q. Does green tea affect fertility?

A. Yes, green tea might induce infertility in men. An excess of flavonoids in green tea causes impaired sperm synthesis, sperm motility and may decrease testosterone levels. On the other hand, in some studies, it is found to affect sperm quality positively. In addition, caffeine may affect the DNA in sperm. The caffeine content in green tea lays out the difficulty in conceiving for women. 

Q. Can green tea reduce belly fat?

A. Some studies have shown that green tea usually reduces body fat, including belly fat. Therefore, consuming green tea in limited amounts can be beneficial during weight loss. In addition, green tea helps improve metabolism in the body, which results in excess burning of calories and hinders fat accumulation.

Q. Is green tea good for PCOS?

A. Research shows that green tea reduces testosterone levels and insulin resistance in women. It can effectively manage PCO cycles. Green tea also has antioxidants which further help with PCOS by reducing the oxidative stress in the body. Oxidative stress is the main reason behind PCOS. 

Q. Is green tea good for females?

A. Yes, for women, green tea has been found exceptionally beneficial. Studies confirm that women who consume green tea reduce their chances of breast cancer by 20-30%. In addition, it has helped in treating arteries and preventing ovarian cancer. But one should check the consumption of green tea while planning to conceive as it may cause fertility issues. 

Q. Is green tea bad for ovarian cysts?

A. No, it’s quite the opposite. Green tea reduces the number of follicles and the number of cysts in the ovary. As a result, it helps improve the overall genital health of females and is beneficial for those with ovarian cysts. 

Q. Is green tea good for the thyroid?

A. While green tea does not have many beneficial properties so far as thyroid problems are concerned, neither does it have any adverse effects. Since it reduces the overall toxicity in the body and maintains a better health condition, it is safe for people with thyroid to consume. 

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