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 5 mechanisms: Additive muscle toxicity, Additive lipid lowering, CYP3A4 induction, CYP3A4 inhibition, and Additive HMG-CoA reductase inhibition. 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
Additive muscle toxicity
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.
Red yeast rice is a statin. It naturally contains monacolin K, the same molecule as the prescription statin lovastatin. Taking it alongside simvastatin means two statins at once. 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 the two without your GP's guidance.
Additive lipid lowering
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.
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.
CYP3A4 induction
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.
CYP3A4 inhibition
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive HMG-CoA reductase inhibition
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.
Other
Statins do reduce plasma CoQ10 levels, but the best-quality randomised trials show that taking CoQ10 alongside a statin does not reliably reduce muscle pain or improve other statin side effects. We treat the pair as safe to combine. If you find it helps you personally that is fine, but the evidence for routine use is weak.
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.
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 methodologyWant this checked across everything you take?
This page checks the pairs you enter. The personalised Distil report goes further:
- the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
- where your current routine may be leaving you short of your goals
- the evidence-backed compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.
See a real sample reportSomething missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.