" 1. Aspirin Some teas, such as cranberry, ginger, and ginkgo biloba, may interact with aspirin and increase the risk of bleeding, particularly when consumed in large amounts.

One serious side effect of aspirin is that it can slow blood clotting, making it easier to bleed, especially in the stomach and brain.

2. Iron Teas high in tannins, such as green and black tea, can reduce iron absorption because tannins form complexes with iron, making it unavailable for use by the body.

This may be especially concerning for people at risk of low iron levels who rely on iron supplements, including women who are menstruating, pregnant people, or those who have just had a baby, or long-distance runners.

However, some researchers found that taking these teas at least one hour before or after taking iron can help reduce complex formation, thereby increasing iron absorption.

3. Folic Acid Some studies suggest that excessive green tea intake can significantly reduce blood folate levels.

Catechins, an antioxidant found in some teas like green and oolong teas, can also reduce how much folate your body can absorb.

As a result, experts advise pregnant women to limit consumption of these teas as they may increase the risk of spina bifida in their babies. Spina bifida is a birth disorder in which the spine doesn’t fully develop, and not getting enough folic acid during pregnancy is a risk factor.

4. Acetaminophen

Some teas, such as Kava tea and hibiscus tea, may affect how Tylenol (acetaminophen) works and increase its side effects.

Acetaminophen and kava both carry a risk of increased liver toxicity, especially when taken in high doses. Therefore, consuming kava tea while taking acetaminophen may further increase your risk of liver injury.

Other teas, such as hibiscus tea, have been found to increase the removal of acetaminophen from the blood, which can make the acetaminophen less effective or cause its effect on pain relief not to last long.

Some researchers recommend taking acetaminophen about 3 to 4 hours before drinking hibiscus tea to avoid shortening the effects of the medication.

5. Omeprazole Some studies have found that teas containing extracts of gingko biloba, goldenseal, and ginger may affect how omeprazole works.

... One serious side effect associated with omeprazole is the risk of bleeding. Since ginkgo biloba extracts have similar side effects, taking them together may increase your risk of bleeding. In addition, teas like golden seal and ginger can also increase stomach acid and interfere with the effectiveness of antacids (medicines used to neutralize stomach acid) and omeprazole.

6. Birth Control Pills Some studies suggest that taking chamomile or St. John's wort along with birth control pills might decrease the effects of birth control pills.

If you are taking any of these supplements, it may help to space them appropriately or, if necessary, switch to a different herbal tea.