The short answer
St John’s wort could plausibly weaken glyburide treatment, but the inspected human studies do not establish this exact pair. Review starting or stopping it and changes in glucose control with the clinician.
What this answer covers
Oral Hypericum perforatum preparations; inducing potential varies with product composition.
- Supplement or preparation
- Hypericum perforatum
- Medication ingredient
- glyburide
The herbal trial used a different sulfonylurea
St John’s wort reduced gliclazide blood exposure in healthy participants, but glucose and insulin measures did not significantly change. Gliclazide is not glyburide.
Glyburide can respond to enzyme-inducing treatment
A separate rifampin study reduced glyburide exposure and glucose lowering. It supports a possible mechanism, but rifampin is not the herb and its measured effect cannot be transferred to St John’s wort.
Absorption loss has not been demonstrated for this pair
Lower blood exposure can result from faster elimination rather than reduced intestinal absorption. Neither inspected study measured the exact glyburide and St John’s wort combination, so a percentage loss or inevitable treatment failure cannot be predicted.
Review changes in either direction
Discuss the product before starting or stopping it and review glucose readings with the diabetes team. Do not self-adjust glyburide or assume that separating doses by a few hours prevents a possible enzyme-mediated effect.
Evidence and practical considerations
Absorption & effectiveness
Exact-pair efficacy/absorption claim is not established by gliclazide plus herb and glyburide plus rifampin studies; narrower mechanistic concern retained with null gliclazide pharmacodynamics.
- Exact scope
- Oral Hypericum perforatum preparations; inducing potential varies with product composition. with Oral glyburide RxCUI 4815 IN, synonym glibenclamide; distinct formulation dosing retained.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair-event rate or arbitrary timing interval.
Factors that may matter: Preparation; Dose; Kidney/liver function; Food intake; Other glucose-lowering treatment.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral glyburide
Glyburide stimulates insulin release and can cause severe hypoglycemia. Renal/hepatic impairment, deficient intake, alcohol and multiple glucose-lowering medicines increase susceptibility. Meal and individualized dose instructions apply.
How this applies: Exact oral glyburide active ingredient and named formulation.
Not glipizide, glimepiride or gliclazide. Formulations have different strengths and prescribing instructions; no supplement-specific adverse-event rate.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral glyburide
Glyburide stimulates insulin release and can cause severe hypoglycemia. Renal/hepatic impairment, deficient intake, alcohol and multiple glucose-lowering medicines increase susceptibility. Meal and individualized dose instructions apply.
How this applies: Exact oral glyburide active ingredient and named formulation.
Not glipizide, glimepiride or gliclazide. Formulations have different strengths and prescribing instructions; no supplement-specific adverse-event rate.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 21 healthy participants.
St John’s wort lowered gliclazide exposure, with no significant glucose or insulin AUC change.
How this applies: Original exposure boundaries retained; not proof of a glyburide-herb outcome.
Gliclazide is not glyburide; healthy short-term study does not establish glyburide efficacy loss.
Source 4: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 10 healthy participants in the glyburide study.
Rifampin lowered glyburide exposure and its glucose-lowering effect.
How this applies: Original exposure boundaries retained; not proof of a glyburide-herb outcome.
Rifampin is not St John’s wort. Magnitude, transporter/enzyme effects and timing cannot be assigned to the herb.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Prepared exact glyburide article distinguishing direct drug warnings, comparator studies and indirect supplement evidence. | |
| Research summary published |
Article revision: 150aebef4c190c51
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.