Are These 5 Common Pet Supplements Safe for Your Cat or Dog?

Many pet supplements are governed by the same regulations as pet food: They do not need to be reviewed, tested, or approved by the Food and Drug Administration before they are sold. And labeling and marketing rules can vary from state to state.

“It’s up to the company to do the necessary studies to prove safety and efficacy, and most do not,” Wakshlag says.

Erratic quality control and lax enforcement can also lead to inaccurate labeling and ineffective or even toxic dosing. “Studies have shown the products claiming to have equal amounts of a particular active ingredient can actually contain drastically different quantities that are much higher or lower than the label states,” Greenstein says, adding that many pet owners wrongly believe that they can give their pets supplements made for humans. “Their dosing needs and metabolism are completely unlike our own,” she says. 

One way to reduce the risks posed by the lack of regulation is to look for products that carry the quality seal of the National Animal Supplement Council (NASC). While it does not indicate that a product is effective, it does show, among other things, that the company passes an independent third-party audit every two years, complies with stringent labeling guidelines, and agrees to submit to random third-party testing to ensure a product’s ingredients meet its label claims. 

“I tell folks to only buy brands with the NASC seal,” Wakshlag says. “Without it, you really don’t know what is in a product or whether it’s safe.”

Some supplements have well-established benefits, such as omega-3s for inflammatory conditions. But many supplements lack sufficient scientific research to support their effectiveness. And weak federal oversight means that companies can get away with making bold marketing claims about their products that are not backed by evidence. 

With so many options on the shelves, it can be hard to tell what’s beneficial vs. what’s buzz. To help you make informed choices, here’s what experts say about the five most common supplements. But remember: The best and safest way to decide whether to give your pet a supplement is to consult your veterinarian and to have them monitor its effect on your pet’s progress.

The claims: Cannabidiol (CBD) products are marketed to promote calm, relieve travel and other stresses, and ease separation anxiety.

What the experts say: “CBD and its derivatives are showing a lot of promise as a new frontier of treatment,” Greenstein says. “There’s enthusiasm for their potential to be helpful in managing numerous diseases, but it’s tempered by the fact that more research needs to be done.” She says that she is optimistic that the research will ultimately support the use of CBD products for a variety of conditions and, ideally, lead to the development of prescription products with a proven track record of safety and efficacy. To understand what this could mean for your pet, consult your vet. 

The claims: Fish oil supplements typically contain omega-3 fatty acids and claim to support joint, skin, and coat health, and to reduce inflammation. 

What the experts say: Long-chain marine fatty acids, such as the omega-3s EPA and DHA, “are very safe and can be effective for a lot of inflammatory conditions when sufficient doses are given,” Wakshlag says. He adds that Omega-3s, which are the most commonly recommended supplements, can also promote neural development in puppies and joint health in all dogs, particularly those with symptoms of osteoarthritis. 

But there are some critical considerations. Doses that are too high can increase the risk of bleeding, cause loose stools, or lead to vitamin E deficiency if not balanced with antioxidants. And some dogs don’t tolerate fish oil well, adds Wakshlag, “so working up slowly is important.” 

Vets also caution that poor quality or improperly stored fish oil can oxidize, and studies have shown that there is a potential harm in consuming oxidized oils.

The claims: Supports hip, joint, and cartilage health.

What the experts say: “Glucosamine is typically formulated with chondroitin and often recommended by vets, but there is no definitive evidence that it will improve arthritis pain in dogs,” Wakshlag says. Naturally occurring glucosamine and chondroitin are components of cartilage. But studies in humans on whether the supplements ease joint pain or help preserve cartilage have been uncertain, and there’s even less research in dogs. "Glucosamine is not going to help with mobility or pain,” says Wakshlag.

The claims: Multivitamins for pets, like those for humans, are designed to fill nutritional gaps. They typically claim to promote healthy skin and coat, and to provide immune system, joint, and digestive support.

What the experts say: Most veterinarians say that multivitamins aren’t necessary if dogs are eating a complete and balanced diet, such as food that meets Association of Animal Feed Control Officials (AAFCO) guidelines. (AAFCO does not approve dog or cat food, but the food label will say if it is formulated to meet AAFCO guidelines.)

“For some pets on homemade, raw, or grain-free diets, supplementation may be necessary to avoid nutritional deficiencies and compensate for missing or underrepresented nutrients,” says Greenstein. (Raw food diets have gained in popularity in recent years, but they come with significant risks for both pets and their owners.) Greenstein cautions that some vitamins, such as vitamin D, can be toxic when given in high doses.

Bottom line: It’s essential to consult your vet before making any dietary changes or introducing vitamin supplements.

The claims: Probiotics usually claim to support digestive and immune health.

What the experts say: While some studies have shown encouraging results, such as aiding in digestion and improving gastrointestinal (GI) issues, including diarrhea, not all vets agree on their effectiveness, and more studies are needed. “To be honest, there is very little evidence to support the use of probiotics for GI issues, including inflammatory bowel disease,” Wakshlag says. “There is little harm in recommending them if people can afford them or want to try an untraditional therapy, but I warn folks that it’s very hit or miss regarding the response.” 

In the end, some supplements can support certain health conditions and promote wellness in pets, as long as they’re used properly and ideally with veterinary guidance. But veterinarians emphasize that nothing beats a balanced diet, regular exercise, vaccinations, and routine checkups as the foundation of a pet’s long-term health.