Since around 3000 BC, people have enjoyed green tea for its many health benefits and its distinctive flavor. In recent years, research has uncovered its supportive connections to weight loss, improved focus, anti-aging effects and cancer prevention. “Green tea is rich in antioxidants and loaded with polyphenols, especially catechins (like EGCG), which can help fight inflammation and reduce oxidative stress,” says Sheeri Jonnala, M.S., RD. But it’s these same bioactive substances in green tea that may cause dangerous interactions with several medications. 

“While green tea is widely considered a healthful beverage, there are certain circumstances where its use may not be appropriate or should be approached with caution,” says Jessica Beal, Pharm.D. Here are five medications that may interact with green tea.

1. Blood Thinners

Anticoagulant medications that thin the blood by reducing the clotting action of vitamin K, like warfarin (also known as Coumadin or Jantoven), may be less effective when taken with large amounts of green tea. One of the most important variables to consider when taking warfarin is the amount of vitamin K you’re consuming through food or supplements, and maintaining a consistent intake. “While the vitamin K content of green tea is much lower than that of leafy greens, large or sudden increases in green tea intake could reduce warfarin’s effectiveness, leading to a risk of clotting,” says Beal.

While a cup or two of green tea is unlikely to affect your INR levels (the measure of how long it takes your blood to clot), cases of reduced warfarin effectiveness have been reported with the intake of one gallon of green tea or more per day.

2. Stimulants

A cup of regular green tea contains about 30 milligrams of caffeine, a nervous system stimulant. While it has less caffeine than what you’ll find in a cup of coffee, it can still add up and interact with other medications that have stimulating effects on the body, such as those used to treat attention-deficit hyperactivity disorder (ADHD). 

“When combined with stimulant medications, there can be an additive effect, leading to elevated heart rate, increased blood pressure, anxiety or insomnia,” explains Beal. If you take a stimulant medication, choosing decaffeinated green tea may be the best option.

3. Iron Supplements

Iron deficiency anemia is a major public health concern, affecting up to 18% of women and a smaller percentage of men around the world. Anemia can lead to extreme fatigue, brittle nails, restless legs and mood disorders, and is often treated with iron supplements to quickly and effectively increase levels.

Unfortunately, drinking green tea may not only interfere with the absorption of iron supplements but may also increase the risk of developing iron deficiency anemia in the first place. While the research is limited and somewhat contradictory, a few studies have found that compounds, including phytates, calcium, tannins, and specific polyphenols in green tea, may limit the absorption of non-heme iron, which is already poorly absorbed by the body., If iron deficiency is a concern, separating green tea from your iron supplements by an hour or two may help eliminate any absorption issues, Beal recommends.

4. Certain Mental Health Medications

Green tea may increase drug levels of antipsychotic medications such as Clozapine (Clozaril) or Olanzapine (Zyprexa) and the antidepressant Amitriptyline (Elavil), explains Beal.,,“Caffeine in green tea is metabolized by the liver enzyme CYP1A2, the same pathway used by these medications,” adds Beal, explaining that the caffeine competes for metabolism, increasing the drug levels and the risk of adverse effects like sedation, significant blood pressure changes or seizures.

Who Should Avoid Green Tea?

Aside from medications, here are some instances where you may want to avoid or limit the amount of green tea you drink: 

• You’re pregnant or breastfeeding: While limiting caffeine to less than 200 to 300 milligrams per day during pregnancy and breastfeeding is recommended, green tea may also affect nutrient availability to a growing fetus. “Green tea can reduce folate absorption, a nutrient crucial for avoiding neural tube defects,” says Jonnala.
• You have anemia: “Green tea contains tannins and catechins that can bind non-heme iron and reduce absorption, making it harder to correct low iron levels,” says Beal.,
• You’re sensitive to caffeine: While green tea has much less caffeine than coffee or energy drinks, it may still impact your sleep, heart rate, anxiety levels or cause migraines if you’re sensitive to its effects. 
• You have hypotension: Green tea catechins have several activities that may reduce blood pressure, with a large review of randomized controlled trials finding that green tea may play a role in lowering both systolic and diastolic blood pressure in people with or without hypertension.

Our Expert Take

Green tea is rich in antioxidants and powerful plant compounds that offer plenty of health perks, but it isn’t completely risk-free. Many of the active compounds in green tea that provide benefits can interfere with certain medications, including blood thinners, stimulants, iron supplements, blood pressure medications, and some mental health drugs. 

Drinking green tea could also do more harm than good if you’re pregnant, caffeine sensitive, have anemia, or struggle with low blood pressure. If you love green tea but take a medication or have a health condition, it’s best to check with your doctor and pharmacist to make sure it’s a safe option.

A small pilot study suggests that pairing a Mediterranean diet with supplements containing phytosterols and omega-3 fatty acids may help improve cholesterol and reduce body fat in menopausal women.

The research published in Frontiers in Nutrition, followed menopausal and perimenopausal women who adapted a Mediterranean-style eating plan and added two daily supplements. One was a phytosterol-based formula containing bergamot, prickly pear extract and vitamin B1. The other was an omega-3 fatty acid supplement, recommended because of its cardiovascular benefits. After just a few months, participants showed improvements in cholesterol levels and body composition.

Menopause often comes with hormonal and metabolic changes that can raise cholesterol, increase abdominal fat and increase cardiovascular risk. Heart disease is the leading cause of death for women, and managing cholesterol is an important part of prevention.

The Mediterranean Diet—built around vegetables, fruits, legumes, whole grains, olive oil and fish—has long been linked to heart health. Phytosterols, or plant sterols, and omega-3s are also well known for helping lower cholesterol and triglycerides. This study set out to see whether combining diet with these supplements could offer extra support during the menopausal transition.

How Was the Study Conducted?

The Italian study team looked at 14 women, 9 of whom were menopausal (with an average age of about 60) and 5 who were perimenopausal (with an average age of about 53). All of them were under the care of a nutrition specialist for dietary intervention due to high cholesterol and weight management. None of the participants were taking lipid-lowering medications or supplements at the start. Each woman received a personalized Mediterranean diet meal plan along with two supplements.

The women were tracked for two to seven months. During that time, researchers measured cholesterol, triglycerides, body weight, waist size and overall body composition.

What Did the Study Find?

At the start, the women had an average BMI of around 27, placing most of them in the overweight or obese category. Their cholesterol profiles showed high total cholesterol and LDL (“bad”) cholesterol, along with low HDL (“good”) cholesterol. About one in five of the menopausal participants also had elevated triglycerides.

After just a few months on the Mediterranean diet meal plan plus the two supplements, the women showed clear improvements across several key markers. Total cholesterol and LDL cholesterol dropped, while HDL cholesterol rose significantly.

The gains in HDL were especially intriguing—up to 65% in menopausal women and 58% in perimenopausal women. These increases are clinically meaningful because low HDL is considered a risk factor for metabolic syndrome and cardiovascular disease. Many women also improved their total cholesterol-to-HDL ratio, lowering it to a range linked with better heart disease prevention.

Researchers also analyzed triglycerides, but the most consistent improvements were seen in cholesterol levels and ratios.

The changes weren’t limited to bloodwork. On average, the women lost body fat, trimmed their waistlines and lowered their BMI. Their waist-to-hip ratios improved as well, suggesting a healthier pattern of fat distribution. In some cases, body fat mass dropped by nearly one-third during the study period.

Like all studies, this one certainly has its limitations—small size being a major one. This study was also conducted in Italy with a group of Italian participants, so it’s difficult to say just how applicable the findings could be to other groups.

How Does This Apply to Real Life

Even though this was a small pilot study, the results match what experts have been saying for years: the Mediterranean diet is one of the best for heart health. Building meals around vegetables, fruits, beans, whole grains, olive oil and fish can go a long way toward keeping cholesterol in check.

Supplements like phytosterols and omega-3s may provide an extra boost, particularly during menopause. And in this study, improvements were seen even though none of the women were taking cholesterol-lowering medications—suggesting that diet and supplements can make a measurable difference.

That said, these aren’t magic pills. How well they work depends on your overall diet, lifestyle, and even your genetics. It’s also important to remember the limitations: this study included just 14 women, didn’t use a control group and only ran for a few months. The results are promising but very preliminary. Larger, longer studies are needed to know whether this combination truly makes a lasting difference.

Our Expert Take

A Mediterranean diet eating pattern remains one of the most reliable ways to support heart health. Supplements, like the ones in the study, may offer additional benefits, but they should be seen as a complement to—not a substitute for—healthy eating and lifestyle habits. A health care professional can help determine whether these options fit into an individual’s overall prevention plan.

The FDA announced they have initiated the approval of leucovorin calcium tablets (Wellcovorin; GSK) for patients with cerebral folate deficiency (CFD), which the agency claims can cause developmental delays with features of autism spectrum disorder (ASD).

The action is based on an FDA-conducted systematic review of published literature between 2009 and 2023, including published case reports and mechanistic data.¹ The autistic features cited by the FDA include seizures and problems with movement and coordination.

GSK, the manufacturer of leucovorin calcium and the holder of the medicine’s new drug application, is working with the FDA on a process to include information needed for the safe use of the drug in patients with CFD on its label. It is unknown how long the approval process may take for leucovorin calcium.¹

What is Cerebral Folate Deficiency?

CFD is a neurological syndrome that begins to impact development at age 2. Low levels of 5-methyltetrahydrofolate, an essential B-vitamin, in the brain can cause CFD. Children may lose some mental and motor skills, while others may experience intellectual disability, difficulty speaking, or recurrent seizures. Motor issues, including tremors or ataxia, can become severe as the disorder progresses. Some research has demonstrated that cerebral folate receptor alpha (FRα) antibodies can be observed in ASD.^2-4

According to the Department of Health and Human Services, autoimmune forms of CFD are the most common presentations. In this form, autoantibodies mistakenly attack the body’s folate transport system, which yields severe neurological symptoms.

It is critical to note that not every individual with ASD harbors FRα autoantibodies. One analysis found that the pooled prevalence of ASD in individuals with CFD was 44%, while the pooled prevalence of CFD in ASD was 38%, with significant variation across included studies. Another found that FRα autoantibodies were identified in 58% to 76% of children with ASD.^3,5,6

What is Leucovorin?

Leucovorin, also known as folinic acid, helps bypass the defective folate transport system and deliver the active form of folate directly to the brain. It is typically used in the treatment of methotrexate toxicity and chemotherapy regimens, while also occasionally used as an alternative agent for megaloblastic anemia when oral intake of folic acid is not possible. It first received FDA approval in 2002.⁷

According to the FDA’s meta-analysis, which encompassed 23 publications over 15 years, leucovorin demonstrated effectiveness in reducing the symptoms of CFD. FDA investigators found that 85% of patients experienced some form of clinical benefit, including improved communication capabilities. Furthermore, efficacy data on the use of leucovorin specifically for the autoimmune presentation of CFD suggest benefits, but the FDA cautions that the data must be replicated in future research.^3,5,7

Some adverse effects are possible with leucovorin but are generally mild in nature. One analysis reported common effects, including aggression, excitement or agitation, headache, insomnia, and increased tantrums. However, these authors concluded that leucovorin appears safe and generally well-tolerated. The FDA stated that leucovorin is generally well-tolerated based on its established safety profile in other approved indications.^3,5,7

What Can Pharmacists Do?

Pharmacists stand to be critical harbingers of trusted, up-to-date medical information in the wake of this announcement. HHS noted in their fact sheet that off-label use of leucovorin has increased substantially in recent years; however, it is critical for pharmacists to explain that ingesting folate through over-the-counter supplements has not been approved by the FDA and may be harmful. Even if a patient presents as using leucovorin, a pharmacist should evaluate their medication history and ensure there are no drug-drug interactions or contraindications that may harm the patient.⁵

Research on this topic is ongoing. The FDA explained in their news release that there are limitations on available data for the use of leucovorin in this population. Pharmacists should counsel patients that, although the FDA is initiating its approval process, leucovorin may not be a stand-alone cure for autistic symptoms. Parents and caregivers of children with ASD should ensure that, above all, the well-being of their child is of top priority, and that novel treatments should be rigorously examined before use.¹

Pharmacists should monitor the approval process of leucovorin and ensure they are prepared to educate patients if and when the drug is made available.

REFERENCES

1. FDA. FDA takes action to make a treatment available for autism symptoms. News Release. Released September 22, 2025. Accessed September 23, 2025. https://www.fda.gov/news-events/press-announcements/fda-takes-action-make-treatment-available-autism-symptoms

2. Cerebral folate deficiency. National Organization for Rare Disorders. Updated August 22, 2019. Accessed September 23, 2025. https://rarediseases.org/rare-diseases/cerebral-folate-deficiency/

3. Rossignol DA, Frye RE. Cerebral folate deficiency, folate receptor alpha autoantibodies and leucovorin (folinic acid) treatment in autism spectrum disorders: A systematic review and meta-analysis. J Pers Med. 2021;11(11):1141. doi:10.3390/jpm11111141

4. Frye RE, Sequeira JM, Quadros EV, et al. Cerebral folate receptor autoantibodies in autism spectrum disorder. Mol Psychiatry. 2012;18(3):369-381. doi:10.1038/mp.2011.175

5. Frye RE, Rossignol DA, Scahill L, et al. Treatment of folate metabolism abnormalities in autism spectrum disorder. Seminars in Pediatric Neurology. 2020;25:100835. doi:10.1016/j.spen.2020.100835

6. Department of Health and Human Services. Autism announcement fact sheet. Released September 22, 2025. Accessed September 23, 2025. https://www.hhs.gov/press-room/autism-announcement-fact-sheet.html

7. Hedge VS, Nagalli S. Leucovorin—StatPearls [Internet]. National Library of Medicine. Last Updated July 3, 2023. Accessed September 23, 2025. https://www.ncbi.nlm.nih.gov/books/NBK553114/