Herbal safety reference
Herb Drug Interaction Checker
Enter what you take. Every result is graded twice — how serious the interaction could be, and how strong the evidence for it actually is.
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Findings
How to read a result
Each finding carries two independent grades. A combination can be theoretically dangerous but barely studied, or well studied and only mildly relevant — collapsing those into one label is how most interaction checkers mislead people.
| 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. |
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 abruptly can push a drug level up as fast as starting it pushed it down.