Milk Thistle (Silybum marianum)
Photo: Unsplash
- Digestive
- 2 conditions
- Licensed photo
Overview
Milk thistle (Silybum marianum, sometimes Carduus marianus) is a tall biennial with spiny, white-veined leaves and purple, thistle-like flower heads. The main constituent of milk thistle extract is silymarin, and milk thistle was historically used for liver disorders and to increase breast milk production. NCCIH says trials in liver diseases, including hepatitis and fatty liver disease, have been conflicting or too limited to reach conclusions.
Traditional uses & properties
Liver Remedy (traditional use): Historically used for liver disorders, which need medical care; NCCIH says trials in liver diseases, including hepatitis, have been conflicting or too limited to reach conclusions. Breast milk (traditional use): Historically used to increase breast milk; NCCIH says it is unclear whether milk thistle has an effect on breast milk production.
Safety & precautions
Side Effects: May cause mild gastrointestinal upset or allergic reactions; MSK advises against it for people allergic to the daisy or ragweed family. Consult Professional: If undergoing chemotherapy or with severe liver conditions, seek guidance on concurrent use.
Educational reference only - not medical advice. Herbs can interact with medications. Consult a qualified healthcare provider before use. Full disclaimer.
Drug interactions
The sources differ. LiverTox finds little evidence of clinically significant herb-drug interactions, while MSK and a systematic review describe several reports. [1, 2]
- HIV medicines
- A 2017 systematic review found some forms of milk thistle significantly lowered levels of certain antiretrovirals. MSK, by contrast, cites a study in which milk thistle did not lower indinavir levels. [2, 3]
- Sirolimus
- MSK says milk thistle may slow sirolimus clearance and advises monitoring, especially in kidney transplant patients who also receive nivolumab. [2]
- Haloperidol, risperidone and aripiprazole
- MSK cites case reports of pancreatitis with haloperidol or risperidone and of liver toxicity with aripiprazole. [2]
- Warfarin
- MSK describes a man on warfarin whose INR rose while he used a liver-cleanse product containing milk thistle and settled after he stopped. [2]
How to read this section: each entry is HerbMate's summary of what the cited sources report. Words such as "may", "theoretical" or "in laboratory or animal studies" mean the effect has not been confirmed in people, and "case report" means it was seen in one or a few patients. A medicine that is not listed here has not been shown to be safe with this herb. The numbers in brackets link to the sources at the foot of the page.
Habitat
Native to the Mediterranean, milk thistle is naturalized in Europe and parts of North America, including California. It grows in sunny, open habitats. Flower heads can be harvested in early summer, and seeds are collected from late summer to early autumn.
Sources
The interaction notes and the statements on this page that name a source were written by HerbMate from these references, which were last checked in October 2026. They are summaries, not medical advice; ask a pharmacist about your own medicines.
Traditionally used for
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Frequently asked questions
What is Milk Thistle (Silybum marianum) traditionally used for?
Traditional sources describe Milk Thistle (Silybum marianum) as follows: Liver Remedy (traditional use): Historically used for liver disorders, which need medical care; NCCIH says trials in liver diseases, including hepatitis, have been conflicting or too limited to reach conclusions. Breast milk (traditional use): Historically used to increase breast milk; NCCIH says it is unclear whether milk thistle has an effect on breast milk production.
What safety cautions apply to Milk Thistle (Silybum marianum)?
Side Effects: May cause mild gastrointestinal upset or allergic reactions; MSK advises against it for people allergic to the daisy or ragweed family. Consult Professional: If undergoing chemotherapy or with severe liver conditions, seek guidance on concurrent use.
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