herbal tea
8 interactions related to herbal tea
turmeric tea + warfarin
Curcumin, the main active compound in turmeric, has antiplatelet and anticoagulant activity in laboratory studies and may inhibit the liver enzymes that clear warfarin. Regulatory case reports describe stable warfarin patients whose INR rose into a dangerous, emergency range within weeks of starting a turmeric product. The published evidence is limited to a small number of case reports, but the bleeding signal is consistent enough to warrant caution.
chamomile tea + warfarin
Chamomile contains naturally occurring coumarin-type compounds and may slow the liver enzymes that clear warfarin, so heavy or sudden chamomile use could add to warfarin's blood-thinning effect. A published case report linked frequent chamomile tea and lotion use to a dangerously high INR and severe internal bleeding in an older woman whose warfarin had previously been stable.
licorice tea + digoxin
Licorice (Glycyrrhiza glabra) contains glycyrrhizin, which inhibits the renal enzyme 11-beta-hydroxysteroid dehydrogenase type 2 and produces mineralocorticoid-like potassium loss. The resulting hypokalemia increases the heart's sensitivity to digoxin, raising the risk of digoxin toxicity and dangerous arrhythmias.
valerian tea + benzodiazepines
Valerian (Valeriana officinalis) appears to act on the same GABA-A receptor system as benzodiazepines, so taking the two together may add to the sedative effect. The human evidence is largely theoretical and case-level, but the plausible result is extra drowsiness, slower reaction time, and more next-day grogginess.
hibiscus tea + hydrochlorothiazide
Hibiscus tea and hydrochlorothiazide both lower blood pressure and act as mild diuretics, so together the effect can be additive on blood pressure and on potassium loss. Animal data also suggest hibiscus may raise hydrochlorothiazide blood levels by reducing its renal clearance, though this has not been confirmed in humans.
peppermint tea + iron
Peppermint tea is rich in plant polyphenols and tannins (including rosmarinic acid) that bind non-heme iron in the gut, forming insoluble complexes the body cannot absorb. Human studies show peppermint tea substantially reduces non-heme iron absorption from a meal, placing it among the stronger natural inhibitors. Heme iron from meat, poultry, and fish is not affected.
rooibos tea + liver enzymes
Rooibos (Aspalathus linearis) is generally well tolerated. A small number of case reports describe transient elevations in liver enzymes (AST, ALT) with heavy or prolonged consumption, though the clearest acute-injury report involved rooibos taken together with another herb rather than rooibos alone. Laboratory (in vitro) work suggests rooibos can modulate hepatic CYP450 enzymes, which raises a theoretical, unproven possibility of affecting the metabolism of some co-administered drugs.
ginger tea + metformin
Ginger (Zingiber officinale) has modest blood-glucose-lowering activity in randomized trials in type 2 diabetes, mainly improving fasting glucose and HbA1c. Combined with metformin the effect is generally additive rather than dangerous. Metformin alone rarely causes hypoglycemia, so the practical concern is small; the risk of a true low rises mainly when ginger is layered onto insulin or an insulin-secreting drug.