What medicine should you not drink green tea with? A comprehensive guide to drug interactions

October 7, 2025 •

4 min read

Green tea is celebrated globally for its potential health benefits, yet compounds like vitamin K, caffeine, and antioxidants can cause significant drug interactions. It is crucial to understand what medicine should you not drink green tea with to prevent serious side effects and reduced medication effectiveness.

Quick Summary

Green tea can interfere with several medications, including blood thinners, statins, and mental health drugs. These interactions can alter drug absorption and effectiveness, or increase the risk of side effects like bleeding or elevated blood pressure. Patients should be aware of these risks and consult a doctor.

Key Points

Blood Thinners and Green Tea: The vitamin K in green tea can counteract blood thinners like warfarin, reducing their effectiveness.
Statins and Absorption: Green tea can decrease the absorption of statins such as atorvastatin, while potentially increasing the blood levels of others like simvastatin.
Mental Health Drug Levels: The caffeine and metabolic effects of green tea can destabilize blood levels of drugs like lithium, clozapine, and MAOIs.
Blood Pressure Medication Interference: Green tea catechins can hinder the absorption of certain beta-blockers and ACE inhibitors, reducing their therapeutic effect.
Stimulant Additive Effects: Combining green tea with stimulant medications can dangerously increase heart rate and blood pressure due to cumulative stimulant effects.
Iron Absorption Reduction: Green tea's polyphenols can inhibit the absorption of iron supplements, which is especially important for individuals with anemia.

Green tea is widely known for its antioxidant properties and other health benefits. However, its active components, such as catechins, vitamin K, and caffeine, can interact with various medications, leading to potential health risks. The severity of these interactions can depend on factors like the amount of green tea consumed, the potency of any extracts, and individual health conditions. This guide explores several medication classes with known interactions.

Blood thinners and green tea

Blood thinners, or anticoagulants and antiplatelet drugs, are used to prevent blood clots. Combining them with green tea can be hazardous.

Warfarin (Coumadin): Green tea contains small amounts of vitamin K, which promotes blood clotting. For patients on warfarin, a consistent daily intake of vitamin K is essential for maintaining therapeutic efficacy. Large or inconsistent consumption of green tea can reduce warfarin's effectiveness, increasing the risk of clots.
Aspirin and NSAIDs: Both green tea and antiplatelet drugs like aspirin and ibuprofen have blood-thinning effects. Taking them together may heighten the risk of bruising and bleeding. This risk is particularly relevant with high green tea intake or concentrated supplements.

Statins and cholesterol medications

Statins are a class of drugs prescribed to lower cholesterol. Green tea can impact their absorption and metabolism.

Atorvastatin (Lipitor): Studies suggest that green tea extract can reduce the absorption of atorvastatin, potentially decreasing its cholesterol-lowering effects.
Rosuvastatin (Crestor): Similarly, green tea polyphenols have been shown to decrease the absorption and effectiveness of rosuvastatin.
Simvastatin (Zocor): For simvastatin, the interaction can be different, with green tea increasing the drug's blood levels in some individuals. This can increase the risk of serious side effects, such as liver damage or rhabdomyolysis (muscle tissue breakdown).

Mental health medications

Green tea's caffeine and other compounds can interfere with the way certain mental health drugs are processed by the body.

Lithium: The caffeine in green tea has a diuretic effect, meaning it increases urination. This can affect the body's lithium levels, and abrupt changes in caffeine intake can cause lithium levels to fluctuate dangerously.
MAOIs (e.g., phenelzine): Monoamine oxidase inhibitors are antidepressants. Combining them with the caffeine in green tea can cause an abnormal spike in blood pressure, potentially leading to a hypertensive crisis.
Clozapine (Clozaril): Caffeine competes for metabolism in the liver using the same enzyme pathway as clozapine. High caffeine intake can increase clozapine levels, raising the risk of adverse effects like sedation or seizures.

Blood pressure medications (Beta-blockers and ACE inhibitors)

Green tea has been shown to reduce the effectiveness of some medications used to treat high blood pressure.

Nadolol (Corgard): Green tea catechins can block the cellular machinery that absorbs nadolol into the bloodstream. This significantly reduces the drug's blood levels and its ability to lower blood pressure effectively.
Lisinopril: Green tea extract may reduce the absorption and effectiveness of this ACE inhibitor, which could lead to an increase in blood pressure.

Stimulant drugs

Since green tea contains caffeine, combining it with other stimulants can result in overstimulation.

ADHD Medications (e.g., Adderall): The additive stimulant effects of green tea and ADHD drugs can lead to an elevated heart rate, increased blood pressure, anxiety, and insomnia.
Ephedrine: Combining caffeine with ephedrine can increase the risk of serious side effects, including high blood pressure and irregular heartbeat.

Chemotherapy agents

Interactions between green tea and chemotherapy drugs are complex and depend on the specific medication. For example, some lab studies suggest potential interactions that can either enhance or diminish the drug's effects. It's crucial for cancer patients to consult their oncologist before consuming green tea or green tea supplements.

Other noteworthy interactions

Iron Supplements: The tannins and polyphenols in green tea can bind to nonheme iron, preventing its absorption in the intestines. Patients with anemia should separate their iron supplement intake from green tea consumption by an hour or two.
Antibiotics: Some antibiotics, particularly quinolones, can slow the body's metabolism of caffeine, increasing the risk of side effects like jitteriness and headache.
Folic Acid: The caffeine in green tea can reduce the absorption of folic acid.
Oral Contraceptives: Estrogen-containing birth control can prolong the time caffeine stays in the body, intensifying caffeine-related side effects like headaches.

Comparison of Major Green Tea Drug Interactions


Medication Class	Example Drugs	Nature of Interaction	Potential Outcome
Blood Thinners	Warfarin, Aspirin	Green tea contains vitamin K (anticoagulants) and has antiplatelet properties (aspirin).	Inconsistent warfarin effectiveness; increased bleeding risk with aspirin/NSAIDs.
Statins	Atorvastatin, Simvastatin	Reduced absorption (atorvastatin) or increased blood levels (simvastatin).	Decreased efficacy (atorvastatin); increased risk of liver damage (simvastatin).
Mental Health Drugs	Lithium, MAOIs, Clozapine	Altered drug levels via diuretic effects or competing metabolism.	Unstable lithium levels; hypertensive crisis (MAOIs); increased side effects (clozapine).
Blood Pressure Drugs	Nadolol, Lisinopril	Inhibited absorption due to catechins.	Reduced effectiveness of blood pressure medication.
Stimulants	Adderall, Ephedrine	Additive stimulant effect from caffeine.	Increased heart rate, blood pressure, anxiety, and insomnia.

Conclusion

While green tea is a popular and healthy beverage for many, it can pose significant risks for individuals taking certain medications. From altering the effectiveness of blood thinners and blood pressure drugs to increasing the potency of stimulants and mental health medications, its compounds can cause a range of adverse effects. It is essential for anyone on medication to consult with their doctor or pharmacist before adding green tea or green tea extract supplements to their diet. An open dialogue with a healthcare provider is the best way to ensure your safety and the effectiveness of your treatment plan.

For more detailed information on herb-drug interactions, you can consult reputable sources like the National Center for Complementary and Integrative Health (NCCIH).

Frequently Asked Questions

If you are on warfarin, you should be very careful with your green tea intake. Since green tea contains vitamin K, it can interfere with the medication's effectiveness. You must discuss your green tea consumption with your doctor to ensure consistent intake and monitor your blood clotting levels.

Yes, green tea can interact with certain blood pressure medications, particularly beta-blockers like nadolol and ACE inhibitors like lisinopril. It can reduce the absorption of these drugs, making them less effective. Consult your doctor if you take these medications.

It depends on the specific antidepressant. For those taking MAOIs, green tea can cause a dangerous spike in blood pressure. For other mental health medications like clozapine, caffeine can increase drug levels and side effects. Always check with your healthcare provider.

Green tea can affect the absorption of some statins (e.g., atorvastatin, rosuvastatin) or increase the blood levels of others (e.g., simvastatin). Excessive consumption is not recommended while on certain statins due to potential liver damage.

You should avoid combining green tea with stimulant drugs for ADHD, such as Adderall, or other stimulants like ephedrine. The caffeine in green tea adds to the stimulant effect, which can increase heart rate, blood pressure, anxiety, and insomnia.

Green tea contains compounds called tannins that can bind to nonheme iron, which is found in plant-based foods and supplements. This reduces the amount of iron your body can absorb. It is best to separate iron supplement intake from green tea consumption by at least an hour or two.

Some antibiotics, specifically quinolones (e.g., ciprofloxacin), can affect how the body metabolizes caffeine. This can lead to increased side effects of caffeine, such as jitteriness. It's best to check with your doctor, especially with higher doses of tea or sensitive individuals.