Levonorgestrel and St Johns Wort

Supplement–drug interaction evidence from the TruthStack database.

SeverityHIGH
Evidence TierNeeds Verification
Interaction TypeANTAGONISTIC
Last Reviewed2026-02-10
Source Verification
Attestation METHODOLOGY_ATTESTED
Corpus manifest 26b2d684...
Last reviewed 2026-02-10
Primary source NCT00131885
Live attestation Query API — returns signed DAA ID per request
Data license CC BY 4.0

Summary

St. John's Wort induces CYP3A4 enzyme activity involved in levonorgestrel metabolism. This database flags that concurrent use is associated with reduced levonorgestrel exposure in published research. Pharmacovigilance data include reports of unintended pregnancies in hormonal contraceptive users taking St. John's Wort. Discuss with your prescriber or pharmacist.

Higher-Concern Contexts

This interaction may be of particular concern in the following contexts:

What We Don't Know

This interaction has needs verification evidence. Key gaps may include: direct clinical trial data for this specific combination, dose-response relationships, and long-term outcome data. Absence of evidence is not evidence of absence.

API Reference

GET https://api.truthstack.co/v1/check?c1=levonorgestrel&c2=st%20johns%20wort

Open, unauthenticated. Returns JSON. Developer documentation

Sources

Primary: NCT00131885

Related Interactions

Methylene Blue + St. John'S Wort Clozapine + St Johns Wort Ethinyl Estradiol + St Johns Wort Phenytoin + St Johns Wort St Johns Wort + Theophylline Amitriptyline + St Johns Wort Citalopram + St Johns Wort Escitalopram + St Johns Wort
What this page is and is not. TruthStack is an informational reference database that describes published pharmacological findings. It does not provide medical advice, diagnosis, or treatment recommendations. The information on this page reflects flags in our database and should not replace consultation with a qualified healthcare provider. Always discuss supplement-drug combinations with your prescriber or pharmacist.