Background

Milk thistle (Silybum marianum) is a plant native to Europe that was brought to North America by early colonists. It seems to help lower blood sugar.

Milk thistle is now found throughout the eastern United States, California, South America, Africa, Australia, and Asia. Its seed might protect liver cells from toxic chemicals and drugs. It may also have antioxidant and anti-inflammatory effects.

People commonly take milk thistle by mouth for diabetes. It is also commonly used for liver disorders, including liver damage caused by alcohol, nonalcoholic fatty liver disease, cirrhosis of the liver, chronic hepatitis, and many other conditions, but there is no good scientific evidence to support many of these other uses.

Don't confuse milk thistle with blessed thistle (Cnicus benedictus).

Safety Safety definitions

When taken by mouth: Milk thistle extract is likely safe for most people. While most people tolerate milk thistle well, it can cause some mild side effects including bloating, indigestion, diarrhea, nausea, and gas.

When applied to the skin: Milk thistle extract is possibly safe when used for short periods of time.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if milk thistle is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Milk thistle is possibly safe when taken by mouth for up to 9 months in children 1 year of age and older.

Allergy to ragweed and related plants: Milk thistle might cause an allergic reaction in people who are sensitive to the Asteraceae/Compositae plant family. This includes ragweed, chrysanthemums, marigolds, daisies, and many others. If you have allergies, be sure to check with your healthcare provider before taking milk thistle.

Hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Milk thistle extracts might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, don't use these extracts.

Effectiveness

Dosing & administration

Milk thistle extracts have most often been used by adults in doses of 140 mg by mouth three times daily for up to 4 years. Milk thistle extracts are usually standardized by the amount of silymarin they contain. This typically ranges from 70% to 80%. Milk thistle is also used in various topical gels and creams.

Milk thistle leaves and flowers are also eaten as a vegetable for salads and used as a substitute for spinach. The seeds are sometimes roasted and used as a coffee substitute.

Interactions with pharmaceuticals

Estrogens

Interaction Rating=Minor Be watchful with this combination.

Milk thistle might decrease the effects of medications providing estrogen by blocking how estrogen works in the body.

Indinavir (Crixivan)

Interaction Rating=Minor Be watchful with this combination.

Milk thistle might increase how quickly the liver breaks down some medications. But milk thistle does not seem to affect how quickly the body breaks down indinavir.

Ledipasvir

Interaction Rating=Moderate Be cautious with this combination.

Taking milk thistle might decrease how quickly the body breaks down ledipasvir. This might increase the effects and side effects of ledipasvir.

Medications changed by the liver (Cytochrome P450 2B6 (CYP2B6) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Milk thistle might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Interaction Rating=Minor Be watchful with this combination.

Some medications are changed and broken down by the liver. Milk thistle might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Interaction Rating=Minor Be watchful with this combination.

Some medications are changed and broken down by the liver. Milk thistle might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Glucuronidated drugs)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Milk thistle might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications for diabetes (Antidiabetes drugs)

Interaction Rating=Moderate Be cautious with this combination.

Milk thistle might lower blood sugar levels. Taking milk thistle along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

Medications moved by pumps in cells (P-glycoprotein substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are moved in and out of cells by pumps. Milk thistle might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Medications used for lowering cholesterol (Statins)

Interaction Rating=Minor Be watchful with this combination.

Milk thistle might change the levels of some medications used for lowering cholesterol (statins). This might decrease how well these medications work.

Morphine

Interaction Rating=Moderate Be cautious with this combination.

Milk thistle might affect levels of morphine in the blood. This might increase or decrease the effects and side effects of morphine.

Raloxifene (Evista)

Interaction Rating=Moderate Be cautious with this combination.

Taking milk thistle might decrease how well the body breaks down raloxifene in the stomach. This might increase the effects and side effects of raloxifene.

Sirolimus (Rapamune)

Interaction Rating=Moderate Be cautious with this combination.

Taking milk thistle might decrease how well the liver breaks down sirolimus. This might increase the effects and side effects of sirolimus.

Sofosbuvir

Interaction Rating=Moderate Be cautious with this combination.

Taking milk thistle might increase how quickly the body breaks down sofosbuvir. This might decrease the effects of sofosbuvir.

Tamoxifen (Nolvadex)

Interaction Rating=Moderate Be cautious with this combination.

Milk thistle might increase how much tamoxifen is absorbed by the body. This might increase the effects and side effects of tamoxifen.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin is used to slow blood clotting. Taking milk thistle might increase the effects of warfarin, which could increase the risk of bleeding.

Interactions with herbs & supplements

Herbs and supplements that might lower blood sugar: Milk thistle might lower blood sugar. Taking it with other supplements with similar effects might lower blood sugar too much. Examples of supplements with this effect include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus.

Interactions with foods

There are no known interactions with foods.