Supplements for Pets: When They Help and When They Don't

Why Pet Supplements Have Exploded in Popularity

The U.S. pet supplement market is estimated to be worth several billion dollars and continues to grow. Owners who prioritize their own wellness naturally extend that thinking to their animals — a reasonable impulse that the supplement industry has been quick to meet with an enormous range of products. Fish oil, probiotics, glucosamine, CBD, digestive enzymes, multivitamins: the list is long and the packaging persuasive.

What's missing from much of that packaging is nuance. Unlike human pharmaceuticals or even pet medications, supplements for animals are not required to demonstrate safety or efficacy before reaching store shelves. The FDA regulates pet supplements under the Federal Food, Drug, and Cosmetic Act as animal feed, but pre-market approval is not required. This means the burden of evaluating a supplement falls largely on the owner — ideally with veterinary guidance. See our common pet nutrition myths guide for context on how marketing claims often outpace the evidence.

Supplements With Meaningful Evidence

Not all supplements are created equal. A handful have accumulated enough research in companion animals to make them credible options in specific situations.

• Omega-3 fatty acids (EPA and DHA): Derived primarily from fish oil, these are the most consistently supported pet supplements. Research suggests benefits for skin and coat health, inflammatory conditions, and possibly cardiac function in cats with certain heart diseases. Dosage matters, however, and fish oil can go rancid — quality and storage are important.
• Glucosamine and chondroitin: Evidence for managing canine osteoarthritis is moderate and mixed, but several studies suggest these compounds may help maintain cartilage and reduce discomfort in dogs with joint disease. They are generally well-tolerated. Results in cats are less clear.
• Probiotics: Certain strains — particularly species-specific formulations — have shown benefit for acute diarrhea and gastrointestinal recovery in dogs. The evidence for long-term systemic benefits is still emerging. Strain specificity matters significantly; a human-formulated probiotic is not equivalent to one designed for dogs or cats.

Where the Evidence Falls Short

Many pet supplements are sold on the basis of theoretical mechanisms or studies in humans, neither of which translates automatically to dogs and cats.

• Multivitamins for healthy pets: A pet eating a diet labeled "complete and balanced" per AAFCO (Association of American Feed Control Officials) guidelines is already receiving adequate vitamins and minerals. Adding a multivitamin can push certain nutrients into excess, and some — like fat-soluble vitamins A and D — are toxic in overdose.
• CBD products: Despite widespread popularity, robust clinical evidence in companion animals remains limited. Some preliminary studies are underway, but veterinarians cannot legally recommend or prescribe CBD in many states, and product purity is inconsistent.
• Herbal and "immune boosting" blends: These categories rarely have species-specific clinical trial data. Some herbal ingredients are actively toxic to pets — certain mushrooms, xylitol-containing products, and some botanical extracts pose real risks.

For pets on homemade diets, the gap between intention and nutritional adequacy is often significant. Our guide to overlooked nutrients in homemade diets outlines the specific deficiencies that arise most often.

How to Evaluate a Supplement Before You Buy

If your veterinarian recommends or approves a supplement, a few quality markers are worth checking:

• Look for a NASC (National Animal Supplement Council) quality seal — this indicates the manufacturer has met specific quality standards and adverse event reporting requirements.
• Check for third-party testing — independent certificate of analysis (COA) verification confirms the product contains what the label claims.
• Confirm species-appropriate formulation — cats have distinct metabolic needs and cannot safely process some ingredients that are harmless to dogs.
• Avoid vague proprietary blends — if the ingredient amounts are hidden behind a "blend" label, assessing safety or efficacy becomes difficult.

The principles of evaluating supplement labels overlap considerably with assessing any pet food. Our practical checklist for evaluating pet food applies many of the same critical-thinking skills. And for broader context on your pet's nutritional foundation, the pet care basics hub is a useful starting point.

This article is for general informational purposes only and does not constitute veterinary advice. Always consult a licensed veterinarian before making changes to your pet's diet or adding any supplement to their regimen.