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Milk Thistle (Silymarin): Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

Quick summary

Milk thistle is the classic 'liver support' herb, built around an antioxidant complex called silymarin. It is plausible and widely used, but high-quality trials have not clearly shown it improves outcomes in liver disease.

What is Milk Thistle (Silymarin)?

Milk thistle (Silybum marianum) is a spiny plant whose seeds yield silymarin, a mix of antioxidant flavonoid compounds (the main one is silybin). It has been used for centuries for liver and gallbladder complaints and is one of the most popular 'detox' and liver-support supplements. It is sold standardised to its silymarin content.

What Milk Thistle (Silymarin) is commonly used for

In supplements, Milk Thistle (Silymarin) is most often included for gut & digestive health support. It is used as nutritional support, not as a treatment for any medical condition — the distinction matters, because the claims on a sales page are often stronger than the evidence allows.

How Milk Thistle (Silymarin) works

Silymarin is an antioxidant that may protect liver cells from damage, help stabilise their membranes, and support cell repair, which is the rationale for milk thistle's liver-protective reputation. These effects are well demonstrated in laboratory and animal models; translating them into clear human benefits has proven harder.

What the evidence says

Here's an honest snapshot of what published research suggests about Milk Thistle (Silymarin) — including where the evidence is limited.

Typical dosage used in studies

Studies commonly use around 140 mg of silymarin two to three times daily (roughly 420 mg/day) of a standardised extract. This is research information, not a recommendation.

Side effects and safety

Milk thistle is generally well tolerated; the most common effects are mild digestive upset and a mild laxative effect. Allergic reactions can occur in people sensitive to the daisy/ragweed plant family.

Medication interactions and who should avoid Milk Thistle (Silymarin)

Medication & safety check

People allergic to ragweed, daisies, marigolds or chrysanthemums may react to milk thistle. It has mild estrogen-like activity in some studies, so those with hormone-sensitive conditions should be cautious, and it may lower blood sugar, which matters for people on diabetes medication. Liver disease should be managed by a doctor, not self-treated with supplements.

This is general information, not personal medical advice. If you take any medication, confirm it's safe to combine with Milk Thistle (Silymarin) with your doctor or pharmacist first.

Sources & further reading

The evidence summary above is drawn from these sources. For general, authoritative background you can also consult:

Frequently asked questions

Does milk thistle 'detox' or repair the liver?

The evidence doesn't support dramatic claims. High-quality trials haven't clearly shown it improves liver-disease outcomes, even though the antioxidant rationale is plausible.

Is it worth taking for liver health?

Some people use it as a low-risk antioxidant, but it is not a proven treatment, and it is not a substitute for medical care for any liver condition.

What dose is used?

Around 420 mg/day of silymarin (often 140 mg three times daily) from a standardised extract.

Who should avoid milk thistle?

People allergic to the ragweed/daisy family, those with hormone-sensitive conditions, and people on diabetes medication should check first.

Does milk thistle interact with medications?

It can mildly affect how some drugs are processed and may lower blood sugar, so review it with a pharmacist if you take regular medication.

Supplements that contain Milk Thistle (Silymarin)

On FactoWiki, Milk Thistle (Silymarin) appears in these reviewed products. Each review breaks down the full formula, pricing and safety.