Guide
Who should not take milk thistle?
People allergic to ragweed and related plants, anyone pregnant or nursing, on prescription medication, or already living with a diagnosed liver or kidney condition should check with a doctor before taking milk thistle.
A National Institutes of Health drug-and-lactation reference database advises avoiding milk thistle if you're allergic to ragweed, daisies, artichokes, common thistle or kiwi — plants in the same family — because cross-reactions, including rare severe ones, are documented. People who are pregnant or nursing, take prescription medication, or already have a diagnosed liver or kidney condition should also check with a doctor first.
Who should be cautious or check with a doctor first
- An allergy to ragweed or other Asteraceae/Compositae-family plants: milk thistle is in the same botanical family as ragweed, daisies, artichokes, common thistle and kiwi, and a reference database that tracks this specifically warns that cross-reactivity, including rare anaphylaxis, is possible — avoid milk thistle if you have a known allergy to any of those.
- Pregnancy or breastfeeding: ask your doctor before using milk thistle if you're pregnant or nursing. One trial found no anomalies with use during pregnancy, but the overall safety data there is limited.
- A diagnosed liver or kidney condition: talk to your doctor before adding milk thistle if you already have a diagnosed liver or kidney condition, since the human research on those populations was run under medical supervision, not as a self-directed addition to existing care — see milk thistle benefits: what the research does and doesn't show for what that research actually found.
- Prescription medication, especially one with a narrow safe-dose range: ask your doctor before combining milk thistle with any prescription medication. See milk thistle and medications: what to check for the specifics.
Questions people ask
Who should not take milk thistle?
People with a known allergy to ragweed or other plants in the same family, and anyone pregnant, nursing, on prescription medication, or already has a diagnosed liver or kidney condition, should check with a doctor before taking it or avoid it, depending on the situation.
Can milk thistle cause liver damage?
No clinical evidence we found shows milk thistle causing liver damage in the doses used in human trials; the research reviewed in milk thistle benefits: what the research does and doesn't show was conducted in people who already had a diagnosed liver condition, monitored by a doctor, not evidence of milk thistle harming a healthy liver.
Does milk thistle help kidneys?
Not reliably — two small trials in people with an existing kidney condition tied to blood sugar reached opposite conclusions, and there's no trial in people without a kidney diagnosis. Milk thistle benefits: what the research does and doesn't show covers both trials in detail.
What shouldn't be taken with milk thistle?
Ask a doctor before combining milk thistle with any prescription medication, since research has found it can change how the body processes certain drugs. Milk thistle and medications: what to check covers the specifics.
When to talk to a doctor
If you have a known allergy to ragweed or a related plant, are pregnant or nursing, take prescription medication, or already have a diagnosed liver or kidney condition, talk to a doctor before starting milk thistle. Milk thistle is not a treatment for a diagnosed liver or kidney condition, and nothing here is a substitute for medical care.
Related reading: milk thistle benefits: what the research does and doesn't show, milk thistle side effects, and milk thistle and medications: what to check.
Sources
- Milk Thistle An NIH reference monograph reports no valid clinical trial support for milk thistle increasing milk supply, describes it as generally well tolerated with occasional GI/skin side effects, and flags rare but real allergic cross-reactivity with ragweed-family plants.
- Addition of silymarin to renin-angiotensin system blockers in normotensive patients with type 2 diabetes mellitus and proteinuria: a prospective randomized trial A larger 2017 trial in people with diabetic kidney disease found no significant difference between silymarin and placebo in kidney function decline, dialysis need or death, though hospitalization rates were lower with silymarin.
- Effect of addition of silymarin to renin-angiotensin system inhibitors on proteinuria in type 2 diabetic patients with overt nephropathy: a randomized, double-blind, placebo-controlled trial A small 2012 trial in people with diabetic kidney disease found 420 mg/day of silymarin for 3 months reduced a urine-protein marker more than placebo, alongside lower inflammation and oxidative-stress markers.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.