Milk Thistle (Silymarin)
Summary
Milk thistle extract (silymarin) is mainly used for the liver. Pooled trials in fatty liver show modest drops in liver enzymes (grade B), but well-run trials in hepatitis C and NASH found no benefit on their main outcomes, and a Cochrane review found no effect on mortality. Small trials suggest lower blood sugar in type 2 diabetes (grade C).
Key facts
- Extract of Silybum marianum; silymarin is a mixture of six major flavonolignans and other polyphenols[9][3]
- 8 RCTs (587 people): ALT −9.2 and AST −6.6 U/L versus control[5]
- In 154 people, 420 or 700 mg three times a day for 24 weeks did not lower ALT more than placebo[2]
- 18 RCTs (1,088 people) with alcohol-related or viral liver disease: no significant effect on mortality, complications or histology[1]
- Bloating, nausea and gas; allergy is possible in people allergic to ragweed, daisies and related plants[9]
- 6 graded human outcomes on this page
- October 11, 2026
How it works
ProposedSilymarin has antioxidant, anti-inflammatory and antifibrotic effects in lab studies. In one NASH trial, fibrosis improved more often than with placebo even though the main activity score did not.[3][9]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Liver | Grade B | Improved | Meta-analysis of 8 trials · n = 587 · 2017 | 5 rows |
| Blood sugar | Grade C | Improved | Meta-analysis of 5 trials · n = 270 · 2016 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Liver enzymes (ALT, AST) in fatty liver disease | Improved | Grade B | Meta-analysis · n = 587 · 2017 Adults with nonalcoholic fatty liver disease Form: Silymarin (various products) · Dose: Varied across trials · Duration: Varied across trials AST −6.57 U/L and ALT −9.16 U/L versus control. | 29245314 (opens PubMed)Source [5] |
| Mortality and complications in alcohol-related or hepatitis B/C liver disease | No effect | Grade C | Systematic review · n = 1,088 · 2007 People with alcoholic and/or viral liver disease Form: Milk thistle extracts · Dose: Varied across trials · Duration: Varied across trials No significant effect on all-cause mortality (RR 0.78), complications or histology; liver-related mortality was lower across all trials but not in the high-quality trials. | 17943794 (opens PubMed)Source [1] |
| Fasting glucose and HbA1c in type 2 diabetes | Improved | Grade C | Meta-analysis · n = 270 · 2016 Adults with type 2 diabetes Form: Silymarin · Dose: Varied across trials · Duration: Varied across trials Fasting glucose −26.9 mg/dL and HbA1c −1.07 points; evidence low quality with high heterogeneity. | 27340676 (opens PubMed)Source [6] |
| Liver histology in NASH (biopsy-proven) | Mixed | Grade C | RCT · n = 99 · 2017 Adults with NASH and NAFLD activity score 4 or more (Malaysia) Form: Silymarin · Dose: 700 mg three times a day (2,100 mg/day) · Duration: 48 weeks Main outcome (30% drop in activity score) did not differ (32.7% vs 26.0%); fibrosis improved in 22.4% vs 6.0%. | 28419855 (opens PubMed)Source [3] |
| Liver histology in NASH without cirrhosis | No effect | Grade C | RCT · n = 78 · 2019 Adults with NASH (US, 5 centres) Form: Silymarin (Legalon) · Dose: 420 or 700 mg three times a day · Duration: 48 weeks Histological improvement in 15% (700 mg), 19% (420 mg) and 12% (placebo); no significant difference. Well tolerated. | 31536511 (opens PubMed)Source [4] |
| ALT in chronic hepatitis C after failed interferon | No effect | No effect | RCT · n = 154 · 2012 Adults with chronic hepatitis C and raised ALT Form: Silymarin · Dose: 420 or 700 mg three times a day · Duration: 24 weeks Only 2 people per group met the ALT goal; no difference in ALT, viral load or quality of life. Side effects matched placebo. | 22797645 (opens PubMed)Source [2] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Standardized silymarin extract (e.g. Legalon) | Varies[2][4] | No head-to-head absorption data in our sources.[2][4] | Side effects similar to placebo at up to 700 mg three times a day for 24–48 weeks.[2][4] | Hepatitis C, NASH, fatty liver, type 2 diabetes |
| Siliphos (milk thistle extract standardized to 33% silybin, with soy lecithin) | Varies[10] | No absorption comparison with standard silymarin in our sources.[10] | Not tested in the trials we cite.[10] | Not tested in the trials we cite |
Studied doses
Doses studied in human trials ranged from 140 mg three times a day (420 mg a day, a 14-day drug-interaction study) to 700 mg three times a day (2,100 mg a day) for 24 to 48 weeks in liver trials.[2][3][4][7]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- LosartanPK studySilymarin 140 mg three times a day for 14 days raised losartan levels and lowered its active metabolite, especially in people with the CYP2C9*1/*1 genotype.[7]
- WarfarinCase reportA case report described INR rising from 2.64 to 4.12 after starting a milk thistle supplement, returning to normal after stopping.[8]
Who should be careful
- Allergy to ragweed, daisies, marigolds or chrysanthemums
- Milk thistle may cause allergic reactions in people allergic to related plants.[9]
- People on warfarin, losartan or other CYP2C9 drugs
- Silymarin changed losartan levels, and a case report linked it to a rise in INR on warfarin.[7][8]
- Pregnancy and breastfeeding
- Little is known about safety in pregnancy or breastfeeding.[9]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Milk Thistle (Silymarin)
Products from brands we partner with that contain Milk Thistle (Silymarin). Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkSilyplus3 capsules: 360 mg Siliphos (120 mg per capsule; milk thistle extract standardized to 33% silybin, about 119 mg silybin a day; also contains soy lecithin); 30 servings. This is a silybin-standardized extract, far below the 1,260–2,100 mg a day of standard silymarin used in the liver trials. Contains soy.Shop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Does milk thistle help the liver?
In fatty liver it modestly lowers liver enzymes. In hepatitis C and NASH, placebo-controlled trials did not show benefit on their main outcomes.[2][4][5]
Does milk thistle lower blood sugar?
A pooled analysis of 5 small trials found lower fasting glucose and HbA1c in type 2 diabetes, but the evidence is low quality.[6][9]
What is the difference between silymarin and silybin?
Silymarin is the whole extract, a mixture of flavonolignans; silybin is one of them. Some products are standardized to silybin instead of silymarin.[3][10]
Does milk thistle interact with medicines?
It raised losartan levels in a study and was linked to a rise in INR on warfarin in a case report.[7][8]
Is milk thistle safe?
It appears well tolerated; digestive upset is most common. Product quality varies, and allergy is possible.[9]
Sources
- [1]Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases.. Cochrane Database Syst Rev, 2007. systematic-review
- [2]Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial.. JAMA, 2012. RCT
- [3]A Randomized Trial of Silymarin for the Treatment of Nonalcoholic Steatohepatitis.. Clin Gastroenterol Hepatol, 2017. RCT
- [4]Silymarin in non-cirrhotics with non-alcoholic steatohepatitis: A randomized, double-blind, placebo controlled trial.. PLoS One, 2019. RCT
- [5]The therapeutic effect of silymarin in the treatment of nonalcoholic fatty disease: A meta-analysis (PRISMA) of randomized control trials.. Medicine (Baltimore), 2017. meta-analysis
- [6]Silymarin in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. J Diabetes Res, 2016. meta-analysis
- [7]Effect of silymarin on the pharmacokinetics of losartan and its active metabolite E-3174 in healthy Chinese volunteers.. Eur J Clin Pharmacol, 2009. PK-study
- [8]CYP2C9-mediated warfarin and milk thistle interaction.. J Clin Pharm Ther, 2020. review
- [9]Milk Thistle: Usefulness and Safety. NCCIH, 2025. fact-sheet
- [10]Silyplus: Supplement Facts. Supersmart, 2026. label
What changed
- First draft. Every PMID checked against NCBI E-utilities (title, year and journal taken from the PubMed record) and abstracts read for each cited row. Product details in Where to buy read from the brand page on the date shown. NCCIH fact sheet (last updated February 2025) read on 2026-10-11. Self-reviewed in a second strict pass, then checked by an independent adversarial fact-check against the PubMed abstracts and live product pages. No credentialed medical reviewer yet.