The short answer
St. John's wort can weaken atorvastatin's cholesterol-lowering effect. Sources support avoidance or clinician review with cholesterol monitoring; spacing the doses has not been shown to prevent the interaction.
What this answer covers
Applies to oral atorvastatin; the direct study tested one St. John's wort product for four weeks, and extract potency can vary.
- Supplement or preparation
- St. John's wort
- Medication ingredient
- atorvastatin
Evidence and practical considerations
Absorption & effectiveness
An exact randomized crossover study demonstrates diminished lipid control, and regulator guidance independently names reduced atorvastatin concentrations.
- Exact scope
- St. John's wort (Hypericum perforatum) with atorvastatin
- Medication form and route
- oral atorvastatin exposure
- Timing or duration
- The exact clinical study evaluated four weeks of St. John's wort during stable atorvastatin therapy; enzyme induction is not limited to same-time administration.
What remains uncertain
- The exact study measured lipids rather than atorvastatin pharmacokinetics.
- Product potency varies substantially among St. John's wort preparations.
- No evidence supports timing separation as a mitigation for enzyme induction.
Factors that may matter: St. John's wort product hyperforin content; duration of use; atorvastatin dose; baseline LDL goal and cardiovascular risk.
Read the supporting source summaries
Source 1: peer-reviewed randomized open crossover human interaction study
pubmed.ncbi.nlm.nih.gov · Source check Jul 24, 2026
Population: Sixteen patients with hypercholesterolemia taking stable atorvastatin 10 to 40 mg daily for at least three months.
Mean LDL increased from 2.34 to 2.66 mmol/L (p=0.004) and total cholesterol from 4.78 to 5.10 mmol/L (p=0.02) during St. John's wort; HDL and triglycerides did not materially change.
Small open study using one commercial product; atorvastatin plasma concentrations were not measured.
Source 2: United Kingdom medicines regulator safety guidance
gov.uk · Source check Jul 24, 2026
Population: Patients receiving atorvastatin or simvastatin.
The guidance explicitly names St. John's wort among CYP3A4 inducers that may reduce atorvastatin plasma concentrations.
Regulatory summary does not quantify the atorvastatin exposure change or specify a product.
Research assessment: · Open full citations ↗
Timing & monitoring
Exact clinical effectiveness loss plus regulator identification of reduced concentrations justifies an actionable avoid-or-monitor instruction, while wording remains conditional because current sources differ in strictness.
- Exact scope
- St. John's wort (Hypericum perforatum) with atorvastatin
- Medication form and route
- oral atorvastatin exposure
- Timing or duration
- Avoidance or lipid monitoring applies during use; same-day separation does not resolve sustained enzyme induction.
What remains uncertain
- Sources differ between avoid, consult, and monitor wording.
- No current U.S. LIPITOR label section naming St. John's wort was identified.
- No evidence supports a fixed dose-separation interval.
Factors that may matter: product hyperforin content; duration; baseline LDL goal; atorvastatin dose.
Read the supporting source summaries
Source 1: United Kingdom medicines regulator safety guidance
gov.uk · Source check Jul 24, 2026
Population: Patients taking atorvastatin.
The guidance names St. John's wort as an inducer that may reduce atorvastatin concentrations.
It does not specify a washout period or a universal management algorithm.
Source 2: peer-reviewed randomized open crossover human study
pubmed.ncbi.nlm.nih.gov · Source check Jul 24, 2026
Population: Sixteen atorvastatin-treated patients with hypercholesterolemia.
LDL and total cholesterol increased significantly during St. John's wort exposure.
Small open study using one product and no atorvastatin concentration measurement.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Research summary published |
Article revision: ec67d72cc9dac7c2
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.
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Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.