The pet supplement market is enormous and largely unregulated. A lot of products make confident claims with thin evidence behind them. Some supplements are genuinely useful. Others are expensive placebos. Here's what current veterinary research actually supports.

The ones with real evidence

Omega-3 fatty acids. Fish oil is one of the most well-studied supplements in veterinary medicine. It supports skin and coat health, has anti-inflammatory properties, and shows real benefit for cats with kidney disease, arthritis, and certain heart conditions. Look for fish oil specifically formulated for cats, or one from a source with a certificate of analysis. Human fish oil capsules work but dosing needs to be adjusted for a cat's weight.

Glucosamine and chondroitin. Commonly used for joint support in older cats and cats with arthritis. The evidence in cats is less robust than in dogs and humans, but it's generally considered safe and many vets recommend it for senior cats showing signs of stiffness or reduced mobility. It's worth a conversation with your vet before starting.

Probiotics. The research here is still developing, but probiotics show genuine promise for cats with digestive issues, stress-related gut problems, and those recovering from antibiotic treatment. Not all probiotic strains work the same way, so look for products that list specific strains and CFU counts.

The ones that need more skepticism

Vitamin and mineral supplements for cats eating a complete and balanced commercial diet are usually unnecessary. Over-supplementing certain vitamins, particularly vitamin A and D, can actually cause harm. Don't add supplements to an already balanced diet without a specific reason and your vet's input.

Herbal supplements marketed for anxiety, immune support, or detox are a mixed bag. Some are harmless. Some interact with medications. Some contain compounds that are toxic to cats. Always check with your vet before giving your cat anything herbal.