Free tool
Herb–Drug Interaction Checker
Never combine a new herb with a prescription drug without checking first. This tool screens your herbs against common medications using interaction data from the American Herbal Pharmacopoeia, ESCOP monographs, Mills & Bone, and peer-reviewed journals.
High-risk
High-risk herb-drug combinations to know
| Drug class | Herbs to screen | Severity |
|---|---|---|
| Warfarin | St John's Wort, ginkgo, garlic, ginger, ginseng, turmeric | Major |
| SSRIs (sertraline, fluoxetine, etc.) | St John's Wort, 5-HTP, SAM-e, tryptophan | Major (serotonin syndrome) |
| Statins (atorvastatin, simvastatin) | Red yeast rice, niacin at high dose | Moderate |
| Immunosuppressants (cyclosporine, tacrolimus) | St John's Wort, echinacea, astragalus | Major |
| Diabetes meds (metformin, insulin) | Bitter melon, cinnamon, fenugreek, gymnema, ginseng | Moderate (additive) |
| Sedatives (benzodiazepines) | Valerian, kava, passionflower, chamomile | Moderate (additive sedation) |
| Blood pressure meds | Hawthorn, licorice (antagonist), yohimbe, ephedra | Major |
| Oral contraceptives | St John's Wort (reduces efficacy), vitex | Major (breakthrough bleeding / pregnancy risk) |
Narrow-therapeutic-index drugs — always talk to your prescriber
For a handful of drugs, even a modest CYP450 shift from an herb can push blood levels into toxic or subtherapeutic range. Do not add any herb to these without discussing with your prescriber:
- Warfarin — bleeding/clotting risk
- Digoxin — cardiac toxicity
- Lithium — toxicity at small dose changes
- Cyclosporine, tacrolimus — transplant rejection risk
- Antiepileptics (phenytoin, carbamazepine) — seizure breakthrough
- Theophylline — toxicity risk
- HIV antiretrovirals — treatment failure