Green Tea Side Effects And Who Must Avoid It


8 Min Read

Green tea is mostly safe for adults when consumed in moderation. But people with stomach problems, iron deficiency, people with low tolerance to caffeine, pregnant or nursing women, people with anemia, anxiety disorders, bleeding disorders, heart conditions, diabetic, liver disease and osteoporosis should not consume green tea as it may have side-effects.

Green tea is one of the oldest herbal teas known to man. It gained quick prominence in the West because of its purported health benefits, weight loss being one of the popular ones. Some of these health benefits are backed by studies while some are not.

Green tea is mostly safe for adults when consumed in moderation. Green tea extract is also considered to be generally safe for most people when taken orally or applied topically on the skin for a short period of time. However, drinking too much green tea (more than 5 cups a day) is considered to be unsafe.

Some people have a natural low tolerance for caffeine, and they will suffer these symptoms even when ingesting small amounts. Some may already be suffering from problems that could be further aggravated by green tea intake. Such people should limit green tea consumption to at most 2 cups per day.

Side Effects of Green Tea

Like all teas, green tea contains caffeine; excessive caffeine intake can lead to or aggravate a variety of problems, including the following:

Stomach Problems

The tannins present in green tea increase stomach acidity that may cause stomach ache, nausea, or constipation. For this reason, green tea is not consumed on an empty stomach in Japan and China.

It is best to drink green tea after a meal or in-between meals. People with peptic ulcers or acid reflux should not consume green tea excessively. A 1984 study concluded that tea is a potent stimulant of gastric acid, which can be reduced by adding milk and sugar.

Sometimes, improper brewing of green tea may also have adverse effects. Green tea is best brewed with water between 160 and 280°F. Excessively hot water may cause heartburn or an upset stomach.

Iron Deficiency and Anemia

Green tea seems to reduce the absorption of iron from food. Drinking very high doses can actually be fatal. The fatal dose of caffeine in green tea is estimated to be 10-14 grams (150-200 mg per kilogram).

Green tea can also reduce the bioavailability of non-heme iron. Non-heme iron is the primary type of iron in eggs, dairy and plant foods such as beans. A 2001 study reports that green tea extract reduces the absorption of non-heme iron by 25%. However, vitamin C increases non-heme iron absorption, so you can squeeze lemon into your tea or consume other vitamin-C rich foods such as broccoli, with your meal.

If you have an iron-deficiency like anemia, the National Cancer Institute recommends consuming tea between meals.

Mild to Serious Headaches

Population-based research studies have shown that caffeine is a risk factor for chronic daily headache onset.1

Sleep Problems, Nervousness and Anxiety

Caffeine exerts obvious effects on anxiety and sleep which vary according to individual sensitivity to methylxanthine.2 It blocks sleep-inducing chemicals in the brain and increases adrenaline production.

Irregular or Accelerated Heartbeat

Caffeine in green tea might cause an irregular heartbeat. It also stimulates the heart muscles to contract when at rest.


Because caffeine affects the movement of food through the food pipe, alternating contraction and relaxation of the food pipe muscles can cause nausea.


Caffeine has a laxative effect. It contributes to peristalsis (the movement of food through the digestive system). It stimulates the colon muscles to contract and then relax, which results in an increased need to move your bowels.

Muscle Tremors and Contractions

By regulating calcium ion channels within cells, caffeine forces skeletal muscle contractions.3


Caffeine increases the release of acid in your stomach. 4 This causes discomfort similar to heartburn.


Caffeine can decrease the flow of blood to the brain, leading to dizziness and motion sickness.5

Ringing in the Ears

Caffeine can aggravate tinnitus or ringing in the ears.6


Caffeine stimulates the central nervous system. It activates neurons when consumed in excess, thus, causing convulsions.7

Bleeding Disorders

Caffeine in green tea might increase the risk of bleeding.


Caffeine in green tea might interfere with blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.


Drinking green tea increases pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.

High Blood Pressure

The caffeine in green tea might increase blood pressure in people with high blood pressure. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.

[Read: Does Green Tea Help Lower Blood Pressure Naturally?]

Liver Disease

Green tea extract supplements have been linked to several cases of liver damage. Green tea extracts might worsen liver disease as the caffeine in the blood may build up and last longer.


Drinking green tea can increase the amount of calcium that is flushed out in urine, which can lead to deterioration of bone health and osteoporosis, especially in those who might be predisposed to the same due to other factors. Caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of green tea). It is possible to make up for some calcium loss caused by caffeine by ingesting calcium supplements.

Pregnancy and Infant Health Risks

Green tea contains caffeine, catechins, and tannic acids. All three substances have been linked to pregnancy risks. If you are pregnant or breastfeeding, green tea in small amounts – about 2 cups per day – is safe. This amount of green tea provides about 200 mg of caffeine. However, drinking more than 2 cups of green tea per day has been linked to an increased risk of miscarriage and other negative effects.

Caffeine passes into breast milk and can affect a nursing infant. In addition, drinking a large amount may cause neural tube birth defect in babies.

Nutrient Absorption Problems in Children

The tannins in green tea may block nutrients absorption such as protein and fats in children. It may also lead to overstimulation because of the caffeine present in green tea.

Can People On Medication Drink Green Tea?

Green tea must not be taken along with these medications as it is known to cause negative reactions:

Highly Interactive

Stimulant drugs like Amphetamines, Nicotine, Cocaine and Ephedrine.

Moderately Interactive

Adenosine, Quinolone antibiotics, Birth control pills, Cimetidine (Tagamet), Clozapine (Clozaril), Dipyridamole (Persantine), Disulfiram (Antabuse), Estrogens pills, Fluvoxamine (Luvox), Lithium, Medications for depression (MAOIs), Hepatotoxic drugs, Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs), Pentobarbital (Nembutal), Phenylpropanolamin, Riluzole (Rilutek),Theophylline, Verapamil and Warfarin.

Slightly Interactive

Alcohol, Fluconazole, Anti-diabetes drugs, Mexiletine (Mexitil) and Terbinafine.

How to Consume Green Tea?

The United Kingdom Tea Council recommends drinking not more than 6 cups of tea a day. For the best health benefits, 3 to 4 cups is recommended. However, doses of green tea vary significantly, but usually range between 1-5 cups daily is considered safe. The commonly used dose of green tea is based on the amount typically consumed in Asian countries, which is about 3 cups per day, providing 240-320 mg of the active ingredients, polyphenols. To make tea, people typically use 1 tsp of tea leaves in 8 ounces of boiling water.

Drink green tea when it’s freshly made but slightly cooled. Scalding tea can damage your digestive system. Moreover, recent studies suggest that too much hot tea can promote throat cancer. Compounds in tea like catechins, theanine, and vitamins C and B diminish over time through oxidation, so the health benefits are strongest with fresh tea. If you’re brewing the same tea leaves, brew them in moderation. With each successive infusion, cancerous substances in the leaves themselves (often pesticides) are drawn out and can even be toxic. Old tea can also harbour bacteria, especially since its antibacterial properties diminish with time.


You don’t have to quit drinking your favourite cup of green tea, but if you have any of the above mentioned medical conditions or taking prescription drugs, exercise caution and consult your doctor about how many cups you can have per day. Moderation is the key to enjoying the full benefits of green tea.

References   [ + ]

1.Scher, Ann I., Walter F. Stewart, and Richard B. Lipton. “Caffeine as a risk factor for chronic daily headache A population-based study.” Neurology 63, no. 11 (2004): 2022-2027.
2.Nehlig A, Davala, Debry G. Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects. Brain Research Reviews. 1992.
3.Kolawole Victor Olorunshola and L.N. Achie. Caffeine Alters Skeletal Muscle Contraction by Opening of Calcium Ion Channels. Current Research Journal of Biological Sciences. 2011.
4.Food and Drug Administration. “Medicines in my home: Caffeine and your body.” US Food and Drug Administration Home Page (2007).
5.Dizziness and Motion Sickness. American Academy of Otolaryngology–Head and Neck Surgery.
6.Goodey, Ron. “Tinnitus treatment–state of the art.” Progress in brain research 166 (2007): 237-246.
7.Nehlig, Astrid, Jean-Luc Daval, and Gérard Debry. “Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects.” Brain Research Reviews 17, no. 2 (1992): 139-170.
CureJoy Editorial

The CureJoy Editorial team digs up credible information from multiple sources, both academic and experiential, to stitch a holistic health perspective on topics that pique our readers' interest.

CureJoy Editorial

The CureJoy Editorial team digs up credible information from multiple sources, both academic and experiential, to stitch a holistic health perspective on topics that pique our readers' interest.

Post a Comment
Freetheplants 5pts

I drink australian sencha green tea every day, I always feel better for doing so, i feel calmer, my skin begins to glow and i have never had stomach cramps. I think where the tea is grown and what is put on it makes a huge difference. Teas grown in places such a china and japan use pesticides regularly, plus pollutants in the area can increase to the toxic nature of these teas. Must be said i love coffee and i substitute sencha green tea to give me that caffeen hit, if you are sensitive to caffeen it will definitely keep you awake.

Rebecca Crigger
Rebecca Crigger 5pts

This is not true, do your own research because this is another way to destroy a natural way of healing and/or living a healthier lifestyle. Do not be fooled by this, do your own research, you do not have to keep spending loads of money on chemically compressed powder in a pill with a crap tone of side effects. I say again do your own research and do not be fooled!

Amanda Pursley
Amanda Pursley 5pts

Hannah Keenan are you still having chest pains? Read this article, particularly the bit about heart muscle contraction.

Hannah Keenan
Hannah Keenan 5pts

I am! I just said then it's really bad again!

Amanda Pursley
Amanda Pursley 5pts

Try cutting down green tea to 3 cups per day this next week and see if it improves x

Mel Halloran
Mel Halloran 5pts

I'd like to add to this list - my doctor told me to avoid both black & green teas as it can contribute to kidney stones. :-( However, herb teas are OK! :-)

Tory Elliott
Tory Elliott 5pts

DThe article failed to mention that teas, including black and green teas, are loaded with calcium oxylate... a major component of most kidney stones. The first thing my urologist said after testing my second stone in two years was to slow down and try to eliminate sources of oxylate in my diet. Due to the cost I must incur while having to have stones removed (they do not pass, I just grow sicker) all teas have promptly left my system... 😢 As much as I LOVE tea, I'm just not willing to risk it.

Anhbuôngtayrồi Đóemcứđiđi
Anhbuôngtayrồi Đóemcứđiđi 5pts

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Feha Khan
Feha Khan 5pts

Arif Sumar thank God I didn't start

Arif Sumar
Arif Sumar 5pts

anything in excess causes One or the other side effects 😒take ✌🏻️ cups a day!

Sahlua Gearon
Sahlua Gearon 5pts

Sian Patrick read this.. maybe we need to cut right back? \U0001f628

Wawan Setiawan
Wawan Setiawan 5pts

Curejoy...I have a really good eyesight!...? and you? jont now... zxQEDnq \U0001f496 start now ->> http://goo.gl/Yc6nxd ... Thanks for view: Green Tea is Not for Everybody - Should You Avoid it? ==> ...curejoy.io/green-tea-side-effects...

Acesmack 5pts

You want this post to get Viral! isn't it ? :D

Parminder Kaur
Parminder Kaur 5pts

I agree, after having green tea empty stomach I got sick.

Dinorah Berrios
Dinorah Berrios 5pts

I like ginger tea...hopefully that is not so controversial ... Drink green tea too...I though it was healthier than soda...

Raveendra Chowdary
Raveendra Chowdary 5pts

Is it healthy to drink one cup of green tea on empty stomach dialy? I am drinking one cup of green tea dialy and immeadieatly eating two bananas is it good or bad?

Cassie Herbst
Cassie Herbst 5pts

Every Time I drink it it makes me extremely sick and my stomach hurts for hours.

Ayurveda 5pts

It is good but exceptions exist in every case! :)

Razia Parbin
Razia Parbin 5pts

And i thought green tea is very healthy and very good for your body

Nonhlar Veeky
Nonhlar Veeky 5pts

Anyone pls......what's the natural way to help a client with piles

Ritu Kumar
Ritu Kumar 5pts

very useful information. Thanks a lot

Nat Dwy
Nat Dwy 5pts

prevents Parkinsons. Just saying

Clare Swirly
Clare Swirly 5pts

Whoa. Only drank it because j thought it was good for you. Ill stick with my lemon water! \U0001f601

Nancy Higdon Taylor
Nancy Higdon Taylor 5pts

Sorry that a side effect is not hilarity!!! All too serious to suit me.

Peggy O'Neill
Peggy O'Neill 5pts

I can't drink it ... when I do my knees seize up.

Karen Smith
Karen Smith 5pts

And I thought it was meant to be good for you, after reading that It sounds very unhealthy

Dianna Lynne
Dianna Lynne 5pts

some rolled their eyes when I said it caused my heart to flutter and blood pressure rise from one cup... just because it didn't effect them

Scott Russell
Scott Russell 5pts

if it's good enough for the healthy living buddist monks,its good enough for me. i drink 2 cups of matcha green tea a day and feel great..

Sue Goodwin
Sue Goodwin 5pts

Can't drink it, gives immediate headache, probably way it's been grown or preserved - additives/preservatives?