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Tea and Medications: Interactions to Ask About |
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Tea feels like the most harmless drink in the world, and for most people it is. But tea contains active natural compounds, including caffeine and flavonoids, and some herbal teas contain plant substances that can affect how medicines work. If you take regular medication for your heart or anything else, it is worth knowing which questions to ask.
This article is for general information only. It is not a complete list of interactions, and it is not a substitute for advice from your doctor or pharmacist.
Why interactions happen
Medicines are absorbed in the gut, processed by the liver and cleared by the kidneys. Some compounds in tea and herbs can influence these steps. They may reduce how much of a drug is absorbed, change how quickly it is broken down, or add to or work against a medicine's effects.
Examples worth discussing
Certain beta-blockers. A clinical study found that drinking large amounts of green tea reduced blood levels of nadolol, a beta-blocker used for high blood pressure and heart conditions. Other medicines may be affected in similar ways.
Blood thinners. Tea leaves contain vitamin K, which plays a role in blood clotting. Brewed tea usually contains only small amounts, but very large amounts of green tea or green tea products have been reported to affect warfarin in some cases. Some herbal products may also influence bleeding risk. If you take a blood thinner, keep your tea habits consistent and tell your care team about any changes.
Stimulant medications and caffeine. Caffeine can add to the effects of other stimulants and of some medicines that raise heart rate. It can also interact with certain antibiotics and other drugs that slow its breakdown.
Iron supplements. Compounds in tea can reduce iron absorption. If you take iron, your doctor may suggest taking it an hour or two apart from tea.
Herbal teas. Hibiscus may add to the effect of some blood pressure and diabetes medicines. Other herbal teas can interact with medicines in different ways, so it is always worth checking.
Green tea extract supplements. Concentrated extracts deliver much higher doses than brewed tea and are more likely to cause interactions and side effects, including rare liver problems.
Practical steps to stay safe
- Make a list of everything you take, including teas, herbal products and supplements, and share it with your doctor and pharmacist.
- Ask specifically whether your tea habit could affect any of your medicines.
- Keep your daily tea intake fairly steady rather than switching suddenly from none to many cups.
- Space tea away from medicines if your pharmacist recommends it.
- Read the information leaflet that comes with your medicines.
Signs to watch for
Contact your doctor if you notice unusual symptoms after changing your tea habits, such as a racing or irregular heartbeat, dizziness, unusual bruising or bleeding, or yellowing of the skin or eyes. Seek emergency care for chest pain or severe symptoms.
The bottom line
For most people, moderate amounts of brewed tea are safe alongside their medicines. Because a few important exceptions exist, the safest approach is to talk openly with your doctor or pharmacist about your tea habits and never stop or change a prescribed medicine on your own.
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