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Milk Thistle for Dogs and Cats

Milk Thistle for Dog and Cat Liver Disease

Milk thistle (Silybum marianum), sometimes also called St. Mary’s thistle, is an herb that has many benefits for dogs and cats. The primary part used is the seeds which are a good source of a complex of flavolignans called silymarin. Standardized milk thistle products may also be referred to as silybin as this is the most active flavolignan in silymarin/milk thistle.

What does milk thistle do for dogs and cats?

Milk thistle's traditional use is as a liver tonic. This is due to the primary active constituent silymarin that research has shown protects liver cells from exposure to disease, such as viral hepatitis, or exposure to toxins from chemicals or poisonous mushrooms. In addition, milk thistle is good for increasing the flow of bile from the liver and gallbladder. This makes it a good choice for a range of liver and gallbladder complaints like hepatitis that is often displayed as high liver enzymes on a blood test.

What is the recommended dosage of milk thistle for dogs and cats?

1). Powder Dosage - 400 mg per 50 lbs twice daily for average daily use and up to 5 grams per 50 lbs daily for therapeutic effects.

2). Alcohol extract - .3 ml per 50 lbs two to three times daily or follow manufacturers directions based on the concentration of their extract.

3). Glycerite - .6 ml per 50 lbs two to three times daily. Keep in mind that some recommend the use of alcohol as the menstruum to extract the full potential of the milk thistle seed. We use heat and glycerin to extract the constituents from the seeds in our Liver Tonic and have had great success with our clients' dogs and cats.

4). Standardized Extract - Approximately 60 mg daily of 80% silymarin standardized extract per 50 lbs and up to 200 mg daily for therapeutic effects.

How long does it take for milk thistle to work in dogs and cats?

Milk Thistle is often recommended when signs of liver disease (hepatitis - liver inflammation) are recognized primarily in the form of high liver enzymes on blood tests. Providing milk thistle will begin to have immediate benefits for the liver. How long this takes to work depends on the damage to the liver and the amount of scar tissue present. Blood tests that measure liver enzymes can be used to measure progress. The wonderful hepatoprotective abilities of milk thistle make it a powerful antidote to amanita (death cap) mushroom poisoning if administered within 24 - 48 hours of ingestion.

How much milk thistle is safe for dogs and cats?

Milk Thistle is a safe and well tolerated herb. No side effects or drug interactions have been reported. Laboratory animals given high doses over long periods displayed no toxicity. Having said that two things should be mentioned. Milk thistle does effect liver metabolism so medication dosages may have to be adjusted when using this herb. In theory milk thistle may lower blood sugar levels so use caution when taking medications or supplements that may also lower blood sugar.

Does milk thistle have any side effects for dogs and cats?

For all its benefits, many herbalists do not recommend that milk thistle be used on a daily basis because of concerns that this may slow the metabolic functions of a healthy liver. This just means that, like everything, don't overdo it for no reason. If you have a healthy animal, using milk thistle for two weeks or so 2 - 4 times per year would be a good idea to maintain liver health. If you have a sick dog or cat you can give them a one week break every 6 - 8 weeks.

Where can I buy milk thistle for my dog or cat?

Right here at The Pet Health and Nutrition Center! We are a small company dedicated to the health and wellness of your dog or cat. We use only USDA organic milk thistle and our glycerites (glycerin tinctures) use organic glycerin USP - most other companies don't match our level of quality. We also have a certified Master Herbalist on staff that formulates all of our herbal remedies along with a certified canine nutritionist to help with any of your questions. We have a couple of great formulas that include milk thistle like our Liver Tonic and organic ground Milk Thistle Seed

What about standardized milk thistle extracts for my dog or cat?

Knowledgeable herbalists like ourselves prefer to use the whole herb as we respect all the constituents in a plant and feel that they work together synergistically to provide beneficial effects on the body. In addition, standardized extracts can often be contaminated by the chemicals solvents used and their quality can vary dramatically with the ethical standards of the company making them. You know what you get when you use whole, organic herbs and we prefer it that way. We waiver slightly in the case of mushroom or other poisoning because a high-quality standardized silymarin extract may be able to minimize liver damage more quickly. However, to receive the benefits of milk thistle for everyday use, such as for its antioxidant, hepatoprotective or liver cell regenerating benefits we would recommend the powder and/or extract of the organic seeds.


Hoffman, D. (2003). Medical herbalism: The science and practice of herbal medicine. Rochester, VT: Healing Arts Press.

Basch, E.M., & Ulbricht, C.E. (2005). Natural standard: Herb & supplement handbook. St. Louis, MO: Mosby.

Tilford, G. L., & Wulff, M. L. (2009). Herbs for pets: The natural way to enhance your pet’s life. (2nd ed.). Irvine, CA: BowTie Press.

About the author

Philip Reich
Philip Reich is a Master Herbalist and co-founder of The Pet Health and Nutrition Center. He specializes in formulating natural, whole food supplements and organic herbal remedies that benefit the health of dogs and cats. The holistic pet health protocols he has developed are followed by clients from all over the world.

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