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Milk Thistle (Silymarin) Side Effects & Safety

Evidence:Strong
·

This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Mild GI discomfort (bloating, diarrhea, nausea) in ~2-10% of users
  • Rare allergic reactions, particularly in people allergic to Asteraceae/Compositae family plants (ragweed, daisies)
  • Mild laxative effect at higher doses
  • Rare headache

Drug & Supplement Interactions

  • May inhibit CYP2C9 and CYP3A4 at high doses — potential interaction with warfarin, statins, and certain medications metabolized by these enzymes
  • May lower blood glucose — monitor closely if taking diabetes medications
  • May reduce effectiveness of oral contraceptives through UGT enzyme induction
  • Theoretical interaction with immunosuppressants (cyclosporine, tacrolimus) — consult physician

Maximum Dose

Do not exceed: 900mg silymarin/day (higher doses used in some clinical trials without adverse effects)

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References

  1. RCTFerenci P, Dragosics B, Dittrich H, Frank H, Benda L, Lochs H, Meryn S, Base W, Schneider B (1989). Randomized controlled trial of silymarin treatment in patients with cirrhosis of the liver. Journal of Hepatology. DOI PubMed
  2. ReviewSaller R, Meier R, Brignoli R (2001). The use of silymarin in the treatment of liver diseases. Drugs. DOI PubMed
  3. Meta-analysisZhong S, Fan Y, Yan Q, Fan X, Wu B, Han Y, Zhang Y, Chen Y, Zhang H, Niu J (2017). The therapeutic effect of silymarin in the treatment of nonalcoholic fatty disease: A meta-analysis (PRISMA) of randomized control trials. Medicine. DOI PubMed
  4. Polyak SJ, Morishima C, Lohmann V, Pal S, Lee DY, Liu Y, Graf TN, Oberlies NH (2010). Identification of hepatoprotective flavonolignans from silymarin. Proceedings of the National Academy of Sciences. DOI PubMed
  5. Moltó J, Valle M, Miranda C, Cedeño S, et al. (2012). Effect of milk thistle on the pharmacokinetics of darunavir-ritonavir in HIV-infected patients.. Antimicrobial agents and chemotherapy. DOI PubMed
  6. Meta-analysisTao L, Qu X, Zhang Y, Song Y, et al. (2019). Prophylactic Therapy of Silymarin (Milk Thistle) on Antituberculosis Drug-Induced Liver Injury: A Meta-Analysis of Randomized Controlled Trials.. Canadian journal of gastroenterology & hepatology. DOI PubMed
  7. Meta-analysisYang Z, Zhuang L, Lu Y, Xu Q, et al. (2014). Effects and tolerance of silymarin (milk thistle) in chronic hepatitis C virus infection patients: a meta-analysis of randomized controlled trials.. BioMed research international. DOI PubMed
Show 5 more references
  1. Rambaldi A, Jacobs BP, Gluud C (2007). Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases.. The Cochrane database of systematic reviews. DOI PubMed
  2. Rambaldi A, Jacobs BP, Iaquinto G, Gluud C (2005). Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases.. The Cochrane database of systematic reviews. DOI PubMed
  3. Rambaldi A, Jacobs BP, Iaquinto G, Gluud C (2005). Milk thistle for alcoholic and/or hepatitis B or C liver diseases--a systematic cochrane hepato-biliary group review with meta-analyses of randomized clinical trials.. The American journal of gastroenterology. DOI PubMed
  4. Jacobs BP, Dennehy C, Ramirez G, Sapp J, et al. (2002). Milk thistle for the treatment of liver disease: a systematic review and meta-analysis.. The American journal of medicine. DOI PubMed
  5. Zare Mehrjerdi P, Asadi S, Ehsani E, Askari VR, et al. (2024). Silibinin as a major component of milk thistle seed provides promising influences against diabetes and its complications: a systematic review.. Naunyn-Schmiedeberg's archives of pharmacology. DOI PubMed