The short answer
St. John’s wort can reduce simvastatin exposure and weaken its cholesterol-lowering effect. Human studies support this concern. Discuss an alternative with your prescriber rather than trying to solve it by taking the herb and medicine a few hours apart.
What this answer covers
Oral Hypericum perforatum products with simvastatin. The studies used specific herb products; other botanicals and other statins are not assumed equivalent.
- Supplement or preparation
- St. John’s wort
- Medication ingredient
- simvastatin
Is there direct evidence?
Yes. In a small volunteer study, two weeks of the herb reduced exposure to simvastatin’s active acid metabolite. This concerns simvastatin specifically; a separate pravastatin group had a different result. It is not appropriate to assign one effect to every statin.
Did cholesterol control change?
A separate twenty-four-person crossover study kept simvastatin doses unchanged. Mean LDL was higher during four weeks of Movina than during the control period. The study was open and product-specific, but it provides a treatment-response signal beyond a laboratory mechanism.
Would spacing or a stronger statin dose help?
The studies did not establish a protective gap. The proposed mechanism involves drug-metabolizing pathways after repeated herb exposure, rather than only contact between two doses in the stomach. Any medication adjustment needs clinician oversight, including when an interacting product is stopped.
What should I discuss before changing anything?
Bring the herb label, daily amount and start date, plus your recent cholesterol results. Your clinician can consider why you use the herb and how to maintain lipid treatment. The evidence does not justify doubling simvastatin or substituting a different statin without a prescription review.
Evidence and practical considerations
Absorption & effectiveness
St. John’s wort can reduce simvastatin exposure and weaken its cholesterol-lowering effect. Human studies support this concern. Discuss an alternative with your prescriber rather than trying to solve it by taking the herb and medicine a few hours apart.
- Exact scope
- Oral Hypericum perforatum products with simvastatin. The studies used specific herb products; other botanicals and other statins are not assumed equivalent. with Exact RxNorm 36567, IN, simvastatin; ZOCOR oral tablets. No substitution of lovastatin, pravastatin or another statin.
- Medication form and route
- oral
What remains uncertain
- Two small studies with specified extracts and limited follow-up. No cardiovascular-event rate, universal low-hyperforin exemption or validated separation schedule is established.
Factors that may matter: Exact preparation, dose, other medicines and baseline clinical condition matter..
Read the supporting source summaries
Source 1: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Eight healthy men received simvastatin; a separate eight-person pravastatin group is not pooled.
Active simvastatin-acid AUC was 48% of placebo, a reduction of approximately 52%.
How this applies: Restricted to the exact identities and conditions described in this article.
Small, preparation-specific pharmacokinetic study; not a cardiovascular-outcome trial.
Source 2: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Twenty-four patients with stable simvastatin 10-40 mg/day.
Mean LDL was 2.72 mmol/L with the herb versus 2.30 mmol/L with control.
How this applies: Restricted to the exact identities and conditions described in this article.
Open study, one product and short follow-up; full PMC/publisher article access failed, so interpretation is limited to the original abstract.
Source 3: regulatory prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed oral simvastatin.
Advises avoiding grapefruit juice and describes dose- and population-qualified niacin muscle precautions.
How this applies: Restricted to the exact identities and conditions described in this article.
Does not establish a numerical risk for every juice, nutritional niacin dose or red yeast rice preparation.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Original-source assessment and consumer article prepared; exact claim dispositions, neutral findings and preparation limits recorded. | |
| Clinical sign-off is pending and no publication approval is asserted. | |
| Research summary published |
Article revision: 4e6c766675b37be6
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.