Supplements and Simvastatin.
Simvastatin, sold under the brand name Zocor, is a statin: it lowers LDL cholesterol by inhibiting HMG-CoA reductase. Statins are the most-prescribed class in the UK.
Simvastatin is the statin most sensitive to CYP3A4 effects, and the one for which supplement and food interactions hit hardest. It is metabolised entirely through 3A4. Anything inhibiting that enzyme raises simvastatin plasma levels, and with them myopathy risk, more sharply than for atorvastatin or rosuvastatin. Grapefruit juice is the textbook example; the BNF and MHRA both flag the combination explicitly. Among supplements, curcumin at higher doses (especially piperine-enhanced or phytosome formulations), quercetin at higher doses, schisandra, and bergamot extract all inhibit 3A4 to varying degrees. The MHRA dose ceiling on simvastatin of 40mg, with limited 80mg use only in specialist settings, reflects this sensitivity. If you are on simvastatin and considering a CYP3A4-active supplement, the cleaner move is often to ask your GP about switching to atorvastatin or rosuvastatin. Both carry lower 3A4 dependence. Statin myopathy still presents the same way. Bilateral proximal muscle ache, sometimes with CK rising on a blood draw.
Below are the 9 documented pairs we have explicitly assessed against Simvastatin in the Distil database: 2 red, 5 amber, and 2 green. The pairs cluster around 6 mechanisms: Additive muscle toxicity, Additive lipid lowering, CYP3A4 induction, CYP3A4 inhibition, Additive HMG-CoA reductase inhibition, and Statin-induced CoQ10 depletion. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 14 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
Additive muscle toxicity
Red Does Niacin interact with ?
High-dose niacin combined with simvastatin raises the risk of severe muscle breakdown (rhabdomyolysis). The FDA has a class warning on this combination. Do not combine.
Evidence: Supported by human study data.
Red Does Red Yeast Rice interact with ?
Taking red yeast rice alongside simvastatin means two statins at once, and simvastatin is one of the more muscle-prone statins, so the combination may raise the risk of muscle damage including the serious form called rhabdomyolysis; do not combine them without your GP's guidance. Red yeast rice naturally contains monacolin K, the same molecule as the prescription statin lovastatin.
Evidence: Well established across multiple human studies or interaction references.
Additive lipid lowering
Amber Does Berberine interact with ?
Berberine lowers LDL cholesterol on its own. Combined with simvastatin the effect is additive. If you take both, ask for a lipid panel sooner than usual after starting so your GP can confirm you are not pushing lipids lower than intended.
Evidence: Limited human data, based on case reports and a known mechanism.
Green Does Beta-Glucan interact with ?
Oat beta-glucan lowers LDL cholesterol by trapping bile acids in the gut, a different route from how a statin works. Taking the two together is complementary, not a harmful clash, and the small extra cholesterol reduction is a benefit. We treat this pair as safe to combine.
Evidence: Supported by human study data.
CYP3A4 induction
Amber Does St John's Wort interact with ?
St John's Wort tends to lower the amount of active simvastatin in your blood, which may reduce its cholesterol-lowering effect. If you take St John's Wort with simvastatin, talk to whoever prescribes it, as your cholesterol may need rechecking.
Evidence: Supported by human study data.
CYP3A4 inhibition
Amber Does Curcumin interact with ?
Curcumin may slow how the body clears simvastatin via CYP3A4. Simvastatin is more sensitive to CYP3A4 inhibition than atorvastatin, so the effect on muscle and liver side-effect risk may be larger. We treat this as a watch-and-tell-your-GP pair.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Quercetin interact with ?
Quercetin may slow how the body clears simvastatin via CYP3A4. Because simvastatin is more sensitive to CYP3A4 inhibition than atorvastatin, the effect may be larger. Watch for muscle pain and tell your GP if you take both.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive HMG-CoA reductase inhibition
Amber Does Bergamot Extract (BPF / Bergavit40) interact with ?
Bergamot's active flavonoids inhibit the same liver enzyme simvastatin targets, so combining them has overlapping mechanisms and no proven additive benefit. The CYP3A4 surface is especially relevant for simvastatin. Discuss with your GP before combining.
Evidence: Limited human data, based on case reports and a known mechanism.
Statin-induced CoQ10 depletion
Green Does Coenzyme Q10 interact with ?
Statins do reduce plasma CoQ10 levels, but replacing it does not reliably ease muscle aches: four analyses of the trials split two against two, the two that measured muscle-damage enzymes found no change, and CoQ10 does not help people stay on their statin. We treat the pair as safe to combine, and it may be worth a trial if you already have statin muscle aches. If you have no symptoms, the evidence does not support taking it routinely.
Evidence: Well established across multiple human studies or interaction references.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyA full supplement review, built around you, not a generic stack.
The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
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