Green Tea Can Interfere With These 9 Medications
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9 Medications That Can Negatively Interact With Green Tea

9 Medications That Can Negatively Interact With Green Tea
Everyday Health
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Updated on August 6, 2025
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Green tea has many health benefits, so it may come as a surprise when your doctor tells you to avoid drinking it with your medications or before surgery.

It turns out that some compounds in green tea can negatively interact with some medications or supplements. And some medications can increase the effects of the caffeine in green tea.

To be safe, always talk to your doctor about whether you can drink green tea with any medication or supplement. Your doctor can let you know about possible side effects and drug interactions before starting the medication.

What Are the Ingredients in Green Tea?

Green tea comes from the leaves of the Camellia sinensis plant. It’s sold in many forms, including liquid extract, capsules, tea bags, loose-leaf tea, and powder. The main active ingredients in green tea are polyphenols — natural compounds found in plants — including epigallocatechin gallate.

Green tea also has tannins and catechins, which are polyphenols that have antioxidant properties.

 Antioxidants are substances found in fruits and vegetables that help protect your cells from damage by free radicals, which could contribute to heart disease, cancer, and other diseases.

Another main ingredient of green tea is caffeine. One 8-ounce (oz) cup has approximately 29 milligrams (mg) of caffeine, which can vary slightly depending on the brand.

Drinking green tea in moderate amounts is generally considered safe, but some green tea extracts and supplements have more concentrated compounds (such as higher levels of caffeine) that can be more likely to interact with medications. Consult your doctor before taking any supplements or herbal remedies, as these are not regulated by the U.S. Food and Drug Administration (FDA) and should be approached with caution before mixing with other supplements or medications.

Medications That Can Interact With Green Tea

There are a few kinds of medication that can negatively interact with the polyphenols and caffeine in green tea. While some only cause a mild interaction, others may potentially cause serious health complications, so talk to your doctor before drinking green tea with any new prescription or supplement.

Some medications that can interact with green tea include the following:

1. Blood Thinners

People who take anticoagulant medications (blood thinners) like warfarin should review their green tea intake with their doctor. Green tea contains vitamin K, which can make the medication less effective, and it has other compounds that might increase the blood-thinning effect of these meds, which can be dangerous. You may be able to drink some green tea while taking blood thinners, but the key is to have a consistent intake of vitamin K in your diet; inconsistency causes shifts in the degree of anticoagulation, potentially lowering the drug’s effectiveness.

2. Statins

Statins are a group of medicines that help reduce low-density lipoprotein (LDL, or “bad” cholesterol) in your blood.

Drinking green tea can possibly reduce the absorption of some statins, like atorvastatin (Lipitor), according to a research study.

Green tea can affect other cardiovascular drugs, too. Polyphenols in green tea have been found to decrease the body’s distribution and absorption of rosuvastatin, a drug used for heart disease as well as for managing cholesterol. On the other hand, green tea extract increases the concentration of the drug sildenafil.

That said, more studies surrounding green tea’s effect on statins are needed to further confirm these findings and to give more accurate guidance for green tea consumption.

3. Aspirin

Both aspirin and certain compounds in green tea can prevent your blood from clotting, and together they may increase your risk of bleeding. This hasn’t been thoroughly researched and applies more if you’re consuming higher doses of green tea or epigallocatechin gallate as a supplement. Discuss with your doctor if you are on aspirin or have cardiovascular or clotting issues and are taking or plan to increase your green tea intake.

4. Certain Mental Health Medications

Green tea can reduce the blood levels of lithium in those who take the medication for mania or bipolar disorder. And if you stop drinking green tea abruptly while on lithium, it can cause your lithium levels to spike.

The caffeine in green tea can also reduce the sedative effects of certain benzodiazepines to treat anxiety, such as alprazolam (Xanax).

When taken with green tea, MAOIs (monoamine oxidase inhibitors) for depression can cause an abnormal spike in blood pressure, leading to a “hypertensive crisis.” Some of these medications include selegiline (Zelapar) and phenelzine (Nardil).

And because green tea acts as a mild stimulant, you shouldn’t drink it alongside other stimulants — like amphetamines (Adderall) for ADHD, for example.

5. Weight Loss Drugs

Ephedrine (Ephedra) is an ingredient that was once often found in weight loss supplements. However, the FDA prohibited the sale of dietary supplements that have ephedra in 2004 because it presents an unreasonable risk of illness.

 There are still forms of it sold outside the United States.
The combination of ephedra — or any stimulant — and caffeine can increase your risk of serious side effects like high blood pressure or irregular heartbeat.

6. Certain Antibiotics

Green tea, specifically the caffeine content, may make a certain class of antibiotics called quinolone antibiotics (which treat a variety of bacterial infections) more effective and increase the risk of side effects while taking them.

 Always talk to your doctor before taking antibiotics with caffeine to make sure there are no interactions.
Some examples of these types of antibiotics include the following:

  • ciprofloxacin (Cipro)
  • enoxacin (Penetrex)
  • grepafloxacin (Raxar)
  • norfloxacin (Chibroxin, Noroxin)
  • sparfloxacin (Zagam)
  • trovafloxacin (Trovan)

7. Beta-Blockers and ACE Inhibitors

The caffeine in green tea may increase blood pressure in people who take beta-blockers for high blood pressure or heart disease. Some of these medications include nadolol, atenolol, and bisoprolol.

A small study also found that taking green tea extract could reduce the absorption and effectiveness of the ACE inhibitor lisinopril (which is prescribed to reduce blood pressure).

8. Iron and Folic Acid

Talk to your doctor if you take iron supplements and want to drink green tea. Green tea can affect the way iron is absorbed in your body.

 The flavonoids in tea can bind to nonheme iron, keeping it from absorbing in your intestines.

Likewise, caffeine can also reduce the absorption of folic acid and may reduce your folic acid levels, especially in people who are pregnant.

9. Certain Herbs

There is some evidence to suggest that drinking caffeine while taking bitter orange extract can increase blood pressure and heart rate.

Talk to your doctor about any herbs or natural supplements you are taking. They can let you know whether you can drink green tea or take green tea extracts while using these substances. Note that supplements are not regulated by the FDA, so just like with green tea, it’s important to make sure they don’t interact with any of your other medications as well.

Does Green Tea Interact With Metformin?

There is no reliable evidence to suggest that metformin (a common diabetes medication) negatively interacts with the caffeine from green tea.

That said, drinking tea is associated with a reduced risk of developing type 2 diabetes. More research is needed to understand this possible association.

Keep in mind that while some people with diabetes can drink caffeine without it affecting their blood sugar, others may notice a spike or dip after drinking it.

If you’re unsure whether you can drink green tea on metformin, talk to your doctor for guidance.

Can You Drink Green Tea Before Surgery?

In your consultation appointment for your surgery, let your doctor know if you drink green tea or take green tea extracts, and ask if you should refrain from drinking it or taking them before your surgery. They can help you figure out what you can and can’t ingest beforehand.

When you’re recovering from surgery, your doctor may suggest you limit caffeine (including from green tea).

How Long After Taking Medicine Can You Drink Green Tea?

There isn’t a specific timeframe laid out by experts regarding how long to wait after taking medicine to drink green tea.

The amount of time you wait to drink green tea will depend on the medication. If you take blood thinners or lithium, for example, you may want to avoid green tea altogether because it may lower (or harmfully increase) the effectiveness of the drugs.

If you’re unsure about how long to wait after taking medication to drink green tea (or any caffeine source, for that matter), talk to your doctor. They can offer tips that address what you’re taking.

When Is the Worst Time to Drink Green Tea?

The worst time to drink green tea will depend on how caffeine affects your body. If you’re sensitive to caffeine, for example, you may want to avoid drinking green tea before bed because it can keep you awake. If you take any of the medications mentioned above, it would be best to wait a few hours before sipping on a cup of green tea.

Who Should Not Drink Green Tea?

Besides people on the medications listed above, there are a few groups of people who may benefit from limiting or avoiding green tea (or its extracts) altogether. These groups include the following:

  • People who are pregnant
  • People who breastfeed or chestfeed
  • Children
  • People with kidney disorders
  • People with heart conditions
  • People with stomach ulcers
  • People with liver problems

Also, people with the following conditions should talk to their doctor before drinking green tea:

  • Anemia

  • Diabetes

The Takeaway

  • Green tea contains polyphenols and caffeine, which may interact negatively with several medications, including blood thinners, statins, and certain antidepressants. Green tea extracts, which can be more potent, may pose a greater risk of interaction than drinking green tea itself.
  • Those taking blood thinners, especially warfarin, should be cautious with their green tea intake because it may decrease the efficacy of the medication or increase the risk of bleeding.
  • Caffeine in green tea can interact with certain drugs, which may amplify caffeine’s effects.
  • Generally, drinking green tea is safe for many individuals and has beneficial antioxidant properties. But those with specific health conditions or taking certain medications should seek medical advice regarding possible interactions, especially for green tea extracts and supplements.

Common Questions & Answers

What happens if I drink green tea every day?
Drinking green tea in moderation every day can have positive effects on your body, such as your heart health, if you don’t take medication (or have a medical condition) that negatively interacts with the beverage.
While not advertised as a diuretic tea, green tea may have a mild diuretic effect (reducing fluid buildup in the body). Green tea has also been used as a diuretic in several traditional Chinese and Indian medicine practices.
For most individuals without prescription medications, green tea is generally safe to consume. Mixed with medications, potential interactions range from mild to potentially severe. Speak with your doctor to learn if you should modify or discontinue your green tea habit.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
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Justin Laube, MD

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Justin Laube, MD, is a board-certified integrative and internal medicine physician, a teacher, and a consultant with extensive expertise in integrative health, medical education, and trauma healing.

He graduated with a bachelor's in biology from the University of Wisconsin and a medical degree from the University of Minnesota Medical School. During medical school, he completed a graduate certificate in integrative therapies and healing practices through the Earl E. Bakken Center for Spirituality & Healing. He completed his three-year residency training in internal medicine at the University of California in Los Angeles on the primary care track and a two-year fellowship in integrative East-West primary care at the UCLA Health Center for East-West Medicine.

He is currently taking a multiyear personal and professional sabbatical to explore the relationship between childhood trauma, disease, and the processes of healing. He is developing a clinical practice for patients with complex trauma, as well as for others going through significant life transitions. He is working on a book distilling the insights from his sabbatical, teaching, and leading retreats on trauma, integrative health, mindfulness, and well-being for health professionals, students, and the community.

Previously, Dr. Laube was an assistant clinical professor at the UCLA Health Center for East-West Medicine and the David Geffen School of Medicine at UCLA, where he provided primary care and integrative East-West medical consultations. As part of the faculty, he completed a medical education fellowship and received a certificate in innovation in curriculum design and evaluation. He was the fellowship director at the Center for East-West Medicine and led courses for physician fellows, residents, and medical students.

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