Supplements for Dogs: What Helps, and Human Supplements That Are Toxic
Fish oil helped dogs with osteoarthritis in veterinary trials. Xylitol, vitamin D and garlic in human products can poison dogs. Always ask your vet first.
By the editorial team · Updated Oct 14, 2026 · 3 sources cited
Among supplements for dogs, fish oil has the best evidence, improving mobility in dogs with osteoarthritis in veterinary trials. Joint supplements and probiotics have limited evidence. Never give dogs human supplements without a vet's advice: xylitol, vitamin D, iron, garlic and onion can poison dogs, sometimes fatally.
Evidence-ranked options
| Supplement | Evidence | Typical dose | Notes |
|---|---|---|---|
| Fish oil (canine osteoarthritis) | C | Dose by weight, as advised by your vet | Improved weight bearing in veterinary trials. |
| Glucosamine/chondroitin | C | Veterinary products | Mixed evidence. |
| Probiotics (veterinary) | C | As directed | Some use for diarrhea. |
| Human supplements | D | Never without a vet | Xylitol, vitamin D, iron, garlic and onion are toxic to dogs. |
A: strong · B: moderate · C: limited or mixed · D: good evidence of no benefit. See the evidence database.
Keep human supplements out of reach
Store vitamins, gummies and sugar-free gum where dogs can't reach them. For people, see our guide to the vitamins most people need.
Frequently asked questions
My dog ate a gummy vitamin. What should I do?
Contact your vet or an animal poison control line immediately. Xylitol-sweetened products can cause life-threatening low blood sugar within minutes.
Are dog supplements regulated?
Quality varies. Choose products recommended by your vet.
Sources
- FDA: Potentially Dangerous Items for Your Pet
- Roush JK et al. Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis. J Am Vet Med Assoc. 2010
- Murphy LA, Coleman AE. Xylitol toxicosis in dogs: an update. Vet Clin North Am Small Anim Pract. 2018
Educational content, not medical advice. Read our medical disclaimer.