Herb Drug Interaction Checker
Add the herbs and medicines you take. Each finding is graded twice: how serious it could be, and how strong the evidence behind it is.
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Findings
How to read a result
Each finding carries two separate grades. A combination can be potentially dangerous but barely studied, or well studied and only mildly relevant. Keeping the two apart shows you which is which.
| Avoid | Do not combine. Documented harm, or a plausible mechanism with severe consequences. |
| Serious | Do not start without your prescriber's agreement. |
| Monitor | May be workable with monitoring, dose adjustment or spacing of doses. |
| Theoretical | Mechanism or scattered reports only. Worth mentioning, not worth panic. |
| No record | Not in this database. Not the same as safe. |
| Evidence A | Human clinical or pharmacokinetic studies. |
| Evidence B | Published case reports or limited human data. |
| Evidence C | Laboratory or animal work only — mechanism, not outcome. |
| Evidence D | Expert opinion or long-standing traditional caution. |
Herb + herb cards come from effects the two herbs share (for example, both thin the blood). They are reasoned from each herb's own evidence, not from studies of the pair, so they are never graded above C.
Live check dot: green means the FDA label names this herb, or PubMed has studies on this exact pair; amber means only the metabolic pathway or the drug class matched; grey means nothing was found live, which is common and not a sign the record is wrong; red means the sources could not be reached.
Why timing matters: enzyme-inducing herbs such as St John's wort keep affecting drug levels for one to two weeks after the last dose. Stopping the herb suddenly can push a drug level up as fast as starting it pushed it down.
About this tool, its limits and sources
What it does. It reports herb–medicine interactions documented in the medical literature and checks each one against the official FDA drug label and PubMed, so you can follow the sources yourself.
What a blank result means. Only that nothing was found. Most herb–medicine combinations have never been studied, so no record is a gap in knowledge, not proof of safety.
What it cannot know. Your dose, your product, your kidney and liver function, or the rest of your medicine list. Herbal products are not standardised: two bottles with the same name can differ tenfold in active content.
Review status. These records have not been individually signed off by a clinician.
Not medical advice. This tool is for education only. Never start, stop or change a prescribed medicine based on it — print your results and take them to your pharmacist or doctor. If you have unusual bleeding, yellowing of the eyes or skin, severe agitation, confusion, a racing heart or fainting, seek urgent medical care.