Milk thistle
Herbal products and dietary supplements
Herbal products and dietary supplements
A herbal supplement (silymarin) widely sold for the liver. Good trials have not shown that it helps liver disease.
Also called: Silybum marianum, silymarin
Quick facts
- Group
- Herbal products and dietary supplements
- Target
- No established target (silymarin extract)
- Used for
- No proven indication · Studied for blood sugar control
- Key effects
- Bloating · Allergic reactions
- Monitor
- Ask every patient about supplements
- ATC
- A05BA03
No doses: the clinician sets them by the current guideline.
Mechanism of action
Milk thistle extract comes from the seeds of Silybum marianum. Its main component is silymarin, a mixture of compounds that is promoted as protecting liver cells. Studies in alcohol-related liver disease, hepatitis B and C and fatty liver disease have given conflicting or inconclusive results, and two NIH-funded trials in hepatitis C and fatty liver found no benefit. Product content can also differ from the label.
- Seed extract rich in silymarin
- Promoted to protect liver cells
- Good trials have not shown benefit
Indications
- No proven indication; studied without clear benefit in chronic liver disease, including fatty liver disease and hepatitis C Metabolic dysfunction-associated steatotic liver disease (MASLD/NAFLD) →
- Studied for blood sugar control in type 2 diabetes; evidence is limited
Adverse effects
- Bloating, nausea and gas
- Allergic reactions, especially in people allergic to ragweed, chrysanthemum, marigold or daisy
Contraindications
- Allergy to plants of the daisy family (Asteraceae)
- Not a substitute for proven treatment of liver disease
Key interactions
- Deferiprone
- Silymarin inhibits UGT1A6, the enzyme that inactivates deferiprone; the combination is avoided
What is monitored
- Ask every patient about supplements, including liver products
- Liver tests are guided by the underlying disease, not by the supplement
Administration and safety
- Sold as a supplement; content and purity can differ from the label, and contamination has been found
- Its use is recorded in the medication history
Pregnancy and breastfeeding
Little is known about its safety in pregnancy or breastfeeding.
Nursing care
- Ask specifically about herbal liver products, which patients often do not mention
- Explain that it has not been shown to treat liver disease
- Ask about allergy to daisy-family plants
Pharmacokinetics
- Absorption
- Taken by mouth as capsules, tablets or extracts; content varies between products
Test yourself
Think of the answer, then tap the question to see it.
What is the main component of milk thistle extract?
Silymarin, a mixture of compounds from the seeds of Silybum marianum.
Has milk thistle been shown to treat liver disease?
No. Results are conflicting or inconclusive, and two NIH-funded trials in hepatitis C and fatty liver found no benefit.
Which iron chelator should not be combined with silymarin, and why?
Deferiprone, because silymarin inhibits UGT1A6, the enzyme that inactivates it.
Connections
← Back to the class: Herbal products and dietary supplements
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Milk Thistle: Usefulness and Safety (National Center for Complementary and Integrative Health (NCCIH), 2025); DailyMed - DEFERIPRONE tablet, coated (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.