Drug & supplement interaction

Milk Thistle + Fluvastatin

Fluvastatin brand names: Lescol, Lescol XL.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Fluvastatin falls into 3 drug categories that Milk Thistle can interact with; the most serious is rated minor. It is unclear if milk thistle inhibits CYP2C9; research is conflicting.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
Interactions3
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Milk Thistle and Fluvastatin

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Milk Thistle interacts with whole categories of medication. Fluvastatin falls into 3 of those categories, so it can interact with Milk Thistle in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Minor).

Minor

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

1 of 3

Why this applies to Fluvastatin

Fluvastatin falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Milk Thistle interacts with.

It is unclear if milk thistle inhibits CYP2C9; research is conflicting.
In vitro research suggests that milk thistle might inhibit CYP2C9. Additionally, 3 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are CYP2C9 substrates, including imatinib and capecitabine. However, contradictory clinical research shows that milk thistle extract does not inhibit CYP2C9 or significantly affect levels of the CYP2C9 substrate tolbutamide. Differences in results could be due to differences in dosages or formulations utilized.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the situation with fluvastatin and milk thistle. Your body clears fluvastatin largely through a liver enzyme called CYP2C9. The thinking is that milk thistle (silymarin) might slow that enzyme down a little, which could let fluvastatin build up slightly higher than usual. If that happened, you'd mainly want to watch for the typical statin complaints, things like muscle aches, soreness, or weakness.

That said, I wouldn't lose sleep over this one. The evidence is genuinely mixed: some lab work hints at a problem, but better human studies suggest milk thistle doesn't meaningfully block CYP2C9. It's rated a minor, unlikely interaction. Still, it's worth a quick mention to your pharmacist or doctor so they know everything you're taking, especially if you notice new muscle pain.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Beckmann-Knopp S, Rietbrock S, Weyhenmeyer R, et al. Inhibitory effects of silibinin on cytochrome P-450 enzymes in human liver microsomes. Pharmacol Toxicol 2000;86:250-6. PubMed
  2. Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo assessment of botanical supplementation on human cytochrome P450 phenotypes: Citrus aurantium, Echinacea purpurea, milk thistle, and saw palmetto. Clin Pharmacol Ther 2004;76:428-40. .
  3. Sridar C, Goosen TC, Kent UM, et al. Silybin inactivates cytochromes P450 3A4 and 2C9 and inhibits major hepatic glucuronosyltransferases. Drug Metab Dispos 2004;32:587-94. PubMed
  4. Doehmer J, Weiss G, McGregor GP, Appel K. Assessment of a dry extract from milk thistle (Silybum marianum) for interference with human liver cytochrome-P450 activities. Toxicol In Vitro 2011;25:21-7. PubMed
  5. Kawaguchi-Suzuki M, Frye RF, Zhu HJ, et al. The effects of milk thistle (Silybum marianum) on human cytochrome P450 activity. Drug Metab Dispos. 2014;42(10):1611-6. PubMed
  6. Pochet S, Lechon AS, Lescrainier C, et al. Herb-anticancer drug interactions in real life based on VigiBase, the WHO global database. Sci Rep 2022;12(1):14178. PubMed
Minor

HMG-CoA REDUCTASE INHIBITORS ("Statins")

2 of 3

Fluvastatin also falls under HMG-CoA REDUCTASE INHIBITORS ("Statins").

Theoretically, milk thistle might interfere with statin therapy by decreasing the activity of organic anion transporting polypeptide 1B1 (OATB1B1) and inhibiting breast cancer resistance protein (BCRP).
Preliminary evidence suggests that a milk thistle extract of silymarin can decrease the activity of the OATP1B1, which transports HMG-CoA reductase inhibitors into the liver to their site of action, and animal research shows this increases the maximum plasma concentration of pitavastatin and pravastatin. The silibinin component also inhibits BCRP, which transports statins from the liver into the bile for excretion. However, in a preliminary study in healthy males, silymarin 140 mg three times daily had no effect on the pharmacokinetics of a single 10 mg dose of rosuvastatin.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the short version on combining milk thistle with your fluvastatin (Lescol). On paper, the silymarin in milk thistle may slow down the transporters that move statins into the liver and out into bile. If that happened, a bit more fluvastatin could linger in your bloodstream, which in theory might raise the chance of statin side effects like muscle aches, soreness, or weakness.

The good news: this is mostly lab and animal data, and a small human study with another statin showed no real change. So this is a theoretical, low-risk concern, not something most people notice. Fluvastatin is active as-is (not a prodrug), so the worry would be a slightly stronger effect, not a weaker one. If you'd like to use milk thistle, just run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Deng JW, Shon JH, Shin HJ, et al. Effect of silymarin supplement on the pharmacokinetics of rosuvastatin. Pharm Res 2008;25:1807-14. PubMed
  2. Bechtold BJ, Lynch KD, Oyanna VO, et al. Rifampin- and Silymarin-Mediated Pharmacokinetic Interactions of Exogenous and Endogenous Substrates in a Transgenic OATP1B Mouse Model. Mol Pharm 2024;21(5):2284-2297. PubMed
Minor

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

3 of 3

Fluvastatin also falls under ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP).

Milk thistle may inhibit one form of OATP, OATP-B1, which could reduce the bioavailability and clinical effects of OATP-B1 substrates.
In vitro research shows that milk thistle inhibits OATP-B1. Two case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are OATP substrates, including sorafenib and methotrexate. OATPs are expressed in the small intestine and liver and are responsible for the uptake of drugs and other compounds into the body. Inhibition of OATP may reduce the bioavailability of oral drugs that are substrates of OATP.
Severity Minor Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with fluvastatin and milk thistle. Fluvastatin needs a transporter called OATP-B1 to get carried into your liver, which is where it actually does its cholesterol-lowering work. In lab studies (not human trials), milk thistle's silymarin seems to block that transporter a bit. The theory is that less fluvastatin reaches the liver, so it might not lower your LDL ('bad cholesterol') quite as well.

I want to keep this in perspective. This is rated minor and rests on test-tube data, so it's far from proven, and fluvastatin isn't a prodrug that gets flipped. Most people won't notice anything. Still, if you're starting milk thistle, mention it to your pharmacist or doctor and keep up with your cholesterol checks so any change shows up.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pochet S, Lechon AS, Lescrainier C, et al. Herb-anticancer drug interactions in real life based on VigiBase, the WHO global database. Sci Rep 2022;12(1):14178. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Milk Thistle Also Interacts With Other Medications

Milk Thistle has 254 moderate, 699 minor known drug interactions in our database — the Fluvastatin one above is among them. If you take anything else, check it against the full list below.

Moderate 254 Minor 699 No known interaction 1,877 (incl. Fluvastatin)
Taking anything else?

Check Another of Your Medications Against Milk Thistle

Covers the 2,830 medications we’ve checked against Milk Thistle. Pick one to open its full report.

From our Q&A

Questions About Milk Thistle or Fluvastatin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Milk Thistle or Fluvastatin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Fluvastatin

This page covers Milk Thistle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fluvastatin page lists 128 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Apple (major), Beer (major), Grapefruit (major) and Siberian Cocklebur (major).

By severity: 7 major · 97 moderate · 24 minor.

Open the Fluvastatin interaction page

One more smart check

Taking Milk Thistle as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,560 real supplement products containing Milk Thistle, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Milk Thistle. Your product may carry other ingredients that interact with Fluvastatin too, on top of Milk Thistle — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Milk Thistle and Fluvastatin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Milk Thistle
Top 5%

#50 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Fluvastatin
Steady interest

#1,919 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Milk Thistle

What is Milk Thistle?

Milk Thistle
  • Liver health and protection
  • Hepatitis
  • Cirrhosis
  • Gallbladder problems
  • High cholesterol
  • Type 2 diabetes support

Milk thistle is a popular herbal supplement most often used for liver health, and its main active component is a group of compounds called silymarin. While it is generally well tolerated, the scientific evidence that it meaningfully improves liver disease or other conditions is mixed and far from conclusive. Talk with your pharmacist or doctor before using it, especially if you have a liver condition or take other medicines.

Read the full Milk Thistle monograph & all interactions
Medication

About Fluvastatin

What Is Fluvastatin Used For?

Brand names: Lescol, Lescol XL

Fluvastatin capsules are used alongside a low-cholesterol diet to lower total cholesterol, LDL-C (bad cholesterol), triglycerides, and a protein called apolipoprotein B, while raising HDL-C (good cholesterol), in adults with primary hypercholesterolemia (high cholesterol) or mixed dyslipidemia (multiple abnormal blood fat levels). Fluvastatin capsules are also approved for children and adolescents aged 10–16 with hereditary high cholesterol (heterozygous familial hypercholesterolemia) when diet alone hasn't worked enough.

In adults who already have clinically evident coronary heart disease (CHD), both fluvastatin capsules and fluvastatin sodium extended-release tablets (including Lescol XL) are used to slow the buildup of plaque in coronary arteries and reduce the risk of needing coronary revascularization procedures (procedures to restore blood flow to the heart). Fluvastatin sodium extended-release tablets and Lescol XL are also approved to reduce LDL-C in adults with primary hyperlipidemia, and in patients aged 10 and older with hereditary high cholesterol who specifically require the higher daily dose.

See full Fluvastatin drug information
Keep checking

Other Drugs & Milk Thistle

Browse every other medication we’ve checked against Milk Thistle — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
254Moderate
699Minor
1,876No known interaction
254 Moderate 699 Minor 1,876 No interaction
Moderate

254 interactions

Showing 60 of 254 moderate interactions — see all 254 on the Milk Thistle page.

Minor

699 interactions

Showing 60 of 699 minor interactions — see all 699 on the Milk Thistle page.

No interaction 1,876 drugs checked — show the list

We also checked Milk Thistle against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,876 medications checked with no known interaction — see the full Milk Thistle list.

See the full Milk Thistle interactions page
See every supplement checked against Fluvastatin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Milk Thistle monograph › Uses, safety, and every drug interaction in one place Fluvastatin supplement interactions › Every supplement checked against Fluvastatin, ranked by severity Fluvastatin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Milk Thistle and Fluvastatin Together: Common Questions

Can you take Milk Thistle with Fluvastatin?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 3 interactions listed for Milk Thistle and Fluvastatin?
Fluvastatin belongs to more than one drug category, and Milk Thistle interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Milk Thistle and Fluvastatin interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.