Supplements
Does Milk Thistle Actually Work for Your Liver?
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20266 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
QUICK ANSWER
Partly. In fatty liver trials, silymarin from milk thistle lowers the liver enzymes ALT and AST more than placebo. The trials are small and their quality is mixed. A Cochrane review of alcohol and hepatitis liver disease found no benefit at all. Measure your ALT rather than guess.
Find the test that measures your liver markers →As of August 2026. Milk thistle is the most searched single supplement we track in the UK. It climbed again this month on the back of a widely shared r/Supplements thread about a month of daily use. The evidence is more interesting than either side of that argument suggests.
Most people who buy it have a specific worry. A heavy year of drinking. A comment from a GP about a fatty liver. A statin, or a course of testosterone. The supplement cannot tell you whether that worry is founded. One number on a blood test can.
1. What is milk thistle sold to do?
Protect the liver. The active part is silymarin, a mix of plant compounds taken from the seeds. UK capsules usually contain 140 mg to 420 mg of it a day.
In the UK it is sold as a food supplement. It is not a licensed medicine here, and it is not a treatment for liver disease.
Two claims sit underneath the marketing, and they need different evidence. One is that it changes numbers on a blood test. The other is that it changes what happens to you. Only the first has held up.
2. Does milk thistle lower liver enzymes?
In fatty liver, usually yes. ALT and AST are enzymes that leak out of liver cells when those cells are stressed, so they are the standard way to watch the organ.
A 2023 systematic review in Cureus pulled together 29 randomised trials covering 3,846 people. The split was this:
A 2024 meta-analysis in Annals of Hepatology pooled 26 trials and 2,375 patients with fatty liver. ALT and AST both fell. Fat visible on biopsy improved as well.
A 2021 meta-analysis in Nutrition found the same drop in transaminases across 8 trials. It held even when people had not lost weight, which is the usual reason a liver enzyme improves.
3. So where does the evidence run out?
At the point that matters most. Lower enzymes are a number. Living longer is an outcome. The two came apart when researchers looked for outcomes.
The Cochrane review pooled 13 trials and 915 patients with alcohol-related or hepatitis B and C liver disease. Milk thistle did not reduce deaths from any cause. Its authors were blunt:
“Our results question the beneficial effects of milk thistle for patients with alcoholic and/or hepatitis B or C virus liver diseases and highlight the lack of high-quality evidence to support this intervention.”
Two trials funded by the US National Institutes of Health point the same way. One in hepatitis C, one in a progressive form of fatty liver, and neither showed a benefit.
The fatty liver meta-analyses are honest about their own weakness too. The Nutrition authors flagged flaws in the quality of the studies they pooled. The 2024 authors wrote that the effects will need confirming by further research.
4. Is milk thistle safe to take?
It has a better safety record than most of the liver aisle. The NIH describes it as well tolerated when taken by mouth. Three things are still worth knowing.
That last point is the irony of the shelf it sits on. Our guide to herbal supplements and liver damage covers the botanicals with reported cases. If you take prescription medicines, ask your pharmacist before you start.
5. Which marker answers the question for you?
ALT. It is the enzyme every one of those trials watched, so it is the one that tells you whether your own liver is doing what theirs did. You cannot feel it. That is the point of measuring it.
The NHS makes the case for testing better than we can:
“Non-alcoholic fatty liver disease is usually diagnosed after blood tests or scans are done for another reason, and the results show signs of problems with your liver.”
Found by accident, in other words. Helvy’s Thyroid & Vital Organs panel (£159) measures ALT, ALP, albumin and total protein from a home finger-prick sample, alongside thyroid, kidney and cholesterol markers.
Two honest limits. AST is not in any Helvy panel, and neither is GGT, the enzyme most people link with alcohol. If GGT is the number you want, ask your GP, or tell us through build my test. Our GGT guide explains what it shows.
If you want the full panel explained first, start with our liver function test guide. A blood test measures biomarkers and offers wellness insight. It does not diagnose liver disease.
6. What moves ALT more than a capsule?
Weight and alcohol, by a distance. The NHS position on fatty liver is that most people need no treatment beyond lifestyle change unless the condition has progressed.
That is not a reason to skip the supplement if you want it. It is a reason not to expect it to carry the whole job. Our guide on how to lower ALT levels sets out what actually shifts the number.
One warning worth repeating. A raised ALT is a reason to see a GP, not a reason to buy a supplement. If you are testing to see whether milk thistle is working, retest after 8 to 12 weeks, and time it using our guide to alcohol before a blood test. The metabolic health hub gathers the rest of the markers in one place.
READY TO TEST?
A supplement cannot tell you how your liver is doing. ALT can.
ALT, ALP, albumin and total protein, alongside thyroid and kidney markers. Results in about 5 working days from UKAS-accredited UK laboratories, read by a qualified clinician.
Frequently asked questions
Does milk thistle lower liver enzymes?
In fatty liver trials it usually does. A 2023 review of 29 randomised trials found 19 reported lower enzymes, 6 found no change and 4 found a rise. The falls are modest and the study quality is mixed.
Does milk thistle repair the liver?
There is no good evidence that it does. The Cochrane review of 13 trials in alcohol-related and hepatitis liver disease found no reduction in deaths, and concluded that high-quality evidence for milk thistle is lacking.
How long does milk thistle take to work?
Trials ran from a few days to 18 months, with most enzyme changes measured over weeks rather than days. If you want to know whether it is doing anything for you, test ALT before you start and again after 8 to 12 weeks.
What are the side effects of milk thistle?
It is generally well tolerated. The most common side effects are digestive: bloating, nausea and wind. People allergic to ragweed, chrysanthemums, marigolds or daisies may react to it. Ask your pharmacist if you take prescription medicines.
Should I take milk thistle after drinking?
The evidence in alcohol-related liver disease is the weakest part of the whole picture. Cutting back on alcohol has far better support than any capsule. If drinking is the worry, a liver panel and a conversation with your GP are the useful next steps.
Which blood test shows if milk thistle is helping?
A liver panel that includes ALT. The Helvy Thyroid and Vital Organs panel measures ALT, ALP, albumin and total protein. AST and GGT are not included in any Helvy panel. Reference ranges vary by laboratory, so read your result against your own lab range.
Related guides
ALT Blood Test UK
The enzyme every silymarin trial measured, and what your number means.
Dandelion Root for Liver Detox
The other liver supplement of 2026, and what its evidence shows.
Fatty Liver Blood Test UK
Why a normal ALT can still miss it.
Liver Function Test UK
What ALT, ALP, GGT, albumin and bilirubin each show.