Milk Thistle

Botanical name(s):

Silybum marianum

Other name(s):

milk thistle, Marian thistle, Mary thistle, silibinin, silicristin, silidianin, silmar, silybin, silybum, silymarin,

General description

Milk thistle is an annual or biennial plant. It has reddish-purple flowers. It grows to 3 feet tall. It’s often considered a weed and is native to Europe. It can also be found in the United States and South America. It grows in dry, rocky soils. Milk thistle seeds (Silybum marianum) have been used for hundreds of years to treat liver and gallbladder disease.

Milk thistle contains a group of bioflavonoids called silymarin. They’re made from the seeds of the thistle. The most active of the group is silybin. These may protect the liver from damage. It works by stopping toxins from attaching to the liver cells. It also stops free radicals. It’s been used to treat toxic mushroom poisoning, cirrhosis, and hepatitis.

Medically valid uses

Within the last 30 years, silybin has been used to protect the liver. It treats liver issues. These include:

  • Mushroom poisoning

  • Viral hepatitis

  • Cirrhosis

  • Alcoholic liver disease

  • Carbon tetrachloride poisoning

  • Medicines that can cause toxicity (acetaminophen)

Milk thistle has been studied to check if it protects liver cells from inflammation. The results are mixed.

A large study looked at the use of milk thistle for hepatitis C. It found that people had fewer symptoms and better quality of life. But there was no change in the level of virus activity or liver inflammation. 

A few early studies suggest that taking 200 mg of silymarin 3 times per day for 4 months with conventional treatment may have health benefits in people with type 2 diabetes. These include decreasing:

  • Fasting blood glucose level

  • Hemoglobin A1C

  • Total cholesterol

  • Low-density lipoprotein cholesterol

  • Triglycerides

More research is needed to verify the validity of these health benefits from milk thistle.

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Milk thistle may protect the kidneys and pancreas against the effects of chemotherapy. It may also protect against breast cancer. Studies are ongoing.

Dosing format

Milk thistle supplements usually come in the form of capsules or tablets. Follow the instructions on the package for the correct dose.

Side effects, toxicity, and interactions

Milk thistle can cause allergic reactions. Your risk may be higher if you’re allergic to other plants in the same family, such as:

  • Ragweed

  • Chrysanthemums

  • Marigolds

  • Daisies

Milk thistle may lower blood sugar levels. If you have diabetes or low blood sugar (hypoglycemia), talk to your healthcare provider before using it. You should also talk to your healthcare provider if you take medicines or supplements that affect blood sugar levels.

Women who are pregnant, breastfeeding, or have hormone sensitive conditions should talk with their healthcare providers before taking any supplements.

Online Medical Reviewer: Bianca Garilli MD
Online Medical Reviewer: Chris Southard RN
Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Date Last Reviewed: 8/1/2023