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Milk Thistle for Dogs: Benefits and Uses

by Emily Shiffer
Reviewed by Sarah Lynn Wallace, DVM on 01.21.2020. Updated on 07.24.2020

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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.

As a dog owner, you may be looking for more natural ways to help with your pet’s health and disease prevention. And like humans, herbal supplements—used under the guidelines of a trusted veterinarian—are legitimate options. 

If your dog struggles with liver problems, milk thistle may be a helpful supplement to implement. 

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

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

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. And the National Institute of Health also notes milk thistle as a treatment for liver disorders like hepatitis and cirrhosis, as well as gallbladder problems.

What is Milk Thistle Good for in Dogs?

Photo of milk thistle

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

Some conditions that milk thistle may help with are:

Milk thistle has been studied on a limited basis in dogs, but 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.

Milk thistle may also be recommended 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.”

How to Give Your Dog Milk Thistle

Woman giving dog supplement

Since milk thistle is not a drug, you do not 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 dog.  

“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.  

“Milk thistle can be given 2-3 times daily,” says Krause.

If you’re hoping to use a milk thistle supplement that is 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

If you plan to give your dog milk thistle, keep an eye out for a few symptoms that may 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 after giving this supplement, speak to your pet’s veterinarian about the reaction before giving it again. 

While silymarin may help your dog, Summers warns it’s not likely to provide a total cure for any disease or liver problem.

“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.”

Selecting Milk Thistle Supplements for Your Dog

When it comes to selecting a milk thistle supplement for your dog, you should do your own research on reputable brands and work with your dog’s vet to find the best source, as manufacturing of pet supplements is not regulated or standardized. 

“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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