herbal tea
8 interactions related to herbal tea
turmeric tea + warfarin
Curcumin, the principal active compound in turmeric, has antiplatelet and anticoagulant activity in vitro (inhibiting thrombin and factor Xa) and inhibits CYP enzymes involved in warfarin metabolism. Case reports describe INR rising above 10 within weeks of starting turmeric in patients on stable warfarin.
chamomile tea + warfarin
Chamomile contains coumarin-like compounds that may potentiate warfarin's anticoagulant effect. A published case report described a 70-year-old woman on stable warfarin who developed retroperitoneal hemorrhage with an INR of 7.9 after using chamomile tea and lotion for upper respiratory symptoms.
licorice tea + digoxin
Licorice (Glycyrrhiza glabra) contains glycyrrhizin, which inhibits renal 11-beta-hydroxysteroid dehydrogenase type 2 and causes potassium loss through mineralocorticoid-like activity. The resulting hypokalemia sharply increases digoxin's binding to cardiac Na/K-ATPase, raising the risk of life-threatening digoxin toxicity and arrhythmia.
valerian tea + benzodiazepines
Valerian (Valeriana officinalis) modulates GABA-A receptors, the same target as benzodiazepines, producing additive central nervous system depression. Co-use can cause excessive sedation, impaired psychomotor performance, and prolonged drowsiness, especially with alcohol or in older adults.
hibiscus tea + hydrochlorothiazide
Hibiscus (Hibiscus sabdariffa) has intrinsic diuretic and antihypertensive activity and animal studies show it increases serum levels of hydrochlorothiazide while reducing its clearance. The combination can produce additive blood pressure lowering and amplified electrolyte loss including hypokalemia.
peppermint tea + iron
Peppermint tea is rich in polyphenols (particularly rosmarinic acid) and tannins that bind non-heme iron in the gut, forming insoluble complexes that cannot be absorbed. Controlled studies show peppermint tea can reduce non-heme iron absorption from a meal by up to 84%.
rooibos tea + liver enzymes
Rooibos (Aspalathus linearis) is generally well tolerated, but rare case reports describe transient elevations in liver enzymes (AST, ALT) and one report describes acute liver injury after heavy consumption. Rooibos can also modulate hepatic CYP450 enzymes in vitro, creating a theoretical risk of altering metabolism of co-administered drugs.
ginger tea + metformin
Ginger (Zingiber officinale) has modest blood-glucose-lowering activity in randomized trials in type 2 diabetes, primarily improving fasting glucose and HbA1c. Combined with metformin, the effect is generally additive rather than dangerous, but it can occasionally contribute to hypoglycemia, particularly with other glucose-lowering drugs or fasting.