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Milk Thistle for Dogs: Benefits and Uses

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  • Milk thistle may be beneficial to dogs with liver problems.
  • Silymarin is the part of the plant that has the beneficial properties.
  • Milk thistle supplements for dogs comes in capsules, liquid, or powder forms.
  • While milk thistle supplements may benefit a dog's liver, they won't cure diseases.
  • Pet owners should speak to a veterinarian before giving a supplement to their dogs.

Dog owners are always on the lookout for more natural ways to help with their pet’s health and disease prevention. If that includes you, herbal supplements like silymarin and milk thistle for dogs could be just what you’re looking for.

Under the guidance of a veterinarian, milk thistle supplements may help your pooch with liver problems, diabetes, and other conditions.

Here’s everything you need to know about milk thistle supplements to help evaluate whether it makes sense for your dog.

What is Milk Thistle?

“Milk thistle (Silybum marianum) is a flowering plant that contains the flavonoid compound silymarin in the seeds,” says Dr. Stacie Summers, veterinarian at Oregon State University’s Carlson College of Veterinary Medicine

Sometimes called “Mary thistle” or “holy thistle,” the plant’s name comes from the white veins found on its large, prickly leaves. But don’t let its sharp exterior fool you: Many believe milk thistle contains powerful healing properties.

According to one comprehensive medical review, milk thistle has been used by humans for more than 2,000 years, specifically for liver and biliary (gall bladder) disorders. The National Institute of Health even notes milk thistle as a treatment for liver disorders like hepatitis and cirrhosis, as well as gallbladder problems.

What is Silymarin?

“Although the terms milk thistle and silymarin are often used interchangeably,” says Summers, “silymarin is the part of the plant that has the beneficial properties.”

Silymarin is extracted from the seeds of the milk thistle plant to harness its medicinal benefits.

Summers says that silymarin has both antioxidant and anti-inflammatory characteristics. “It has been used as an herbal remedy for various health concerns for centuries,” she says.

What is Milk Thistle Good for in Dogs?

Photo of milk thistle

Summers explains that silymarin and milk thistle for dogs may be beneficial to pups with liver problems and other diseases.  

Some conditions that milk thistle may help with are:

  • Acute or chronic hepatitis
  • Cushing’s disease
  • Diabetes
  • Pancreatitis

Milk thistle has been studied on a limited basis as a liver supplement for dogs, but the results are promising.

A study published in the Journal of Veterinary Pharmacology and Therapeutics found that milk thistle effectively treated liver dysfunction in Beagles.

“Silymarin is believed to inhibit inflammatory pathways, act as an antioxidant by scavenging free radicals that can damage cells, increase protein production by the liver, and promote bile flow,” says Summers.  

For Cushing’s disease in dogs, milk thistle can help protect the liver, says Dr. Angie Krause, a holistic veterinarian at Boulder Holistic Vet in Boulder, Colorado. “While milk thistle will not treat the cause of Cushing’s disease, it can help protect the liver from the increased levels of cortisol,” she says.

Some veterinarians even recommend milk thistle and silymarin as a treatment for diabetes and pancreatitis in dogs. 

“Milk thistle may slightly reduce the insulin needs in diabetic dogs,” says Krause. “It may also be beneficial in the treatment of pancreatitis—both to protect the liver from pancreatic inflammation and promote the smooth flow of bile.”

Milk thistle has also been found to potentially have anticancer properties, and is sometimes used with chemotherapy treatment.

Giving Your Dog Milk Thistle

Woman handing out milk thistle supplement for dogs

Since milk thistle is not a drug, you don’t need a prescription to get it. But as with all supplements for dogs, you should speak to your veterinarian about dosing recommendations for your specific pup.  

“Milk thistle comes in capsules, liquid, or powder,” says Krause. 

For dogs, silymarin is given as an oral supplement, usually via a pill or capsule.  

How much milk thistle for dogs is appropriate? According to Krause, “Milk thistle can be given 2-3 times daily.”

If you’re hoping to use a milk thistle supplement formulated for humans, you should be extra cautious. Speak to your veterinarian before using any human-grade supplement for pets, since they may contain other additives or the dose may not align with your dog’s needs.  

“It depends on the concentration of the product and the size of the dog,” says Krause. “For example, a 5-pound poodle may not be able to consume a supplement meant for a 150-pound human, while a 75-pound dog may easily be able to be dosed from the same bottle as their guardian.”

Side Effects of Milk Thistle for Dogs

Closeup of milk thistle plant

Planning to give your dog a milk thistle supplement? Keep an eye out for side effects that indicate you should stop its use.

“Silymarin is generally safe to give to dogs,” says Summers. “At high doses, silymarin may cause diarrhea in dogs.” If your dog gets diarrhea as a side effect of milk thistle, speak to your veterinarian about the reaction before giving it again. 

Even though silymarin may be a beneficial liver supplement for dogs, it won’t likely provide a longterm cure.

“While silymarin may be beneficial in dogs with inflammatory liver conditions, it is unlikely to cure a pet of the disease by itself,” she says. “I think of silymarin as a liver protectant that should be given while the underlying condition is diagnosed and treated directly with appropriate therapy, especially in dogs with chronic liver enzyme elevations.”

Choosing a Milk Thistle Supplement for Your Dog

When it comes to selecting a milk thistle or other liver supplement for your dog, do your research. Manufacturing of pet supplements is not regulated or standardized, so only buy from reputable brands and consult your dog’s vet.

“Herbal supplements are not held to the same efficacy standards as other medications and the potency, purity, and bioavailability varies between manufacturers,” says Summers. “I would recommend that pet owners use dog-specific products from a reputable manufacturer that are recommended by their veterinarian and contain the appropriate amount of bioavailable silymarin (in addition to the liver protectant SAMe) to maximize the chances of silymarin working for their pet.”

Krause says the label should clearly state the amount of milk thistle or silymarin in the product. “You can ask the manufacturer to provide a certificate of analysis of the product,” she says, which can help determine its purity. “Or purchase a product directly from your veterinarian.”


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