Yellow: with caution
A small bite will not hurt, but tuna should not be a regular food. It is not toxic like onions or chocolate. The problem is mercury.
Why it gets a yellow rating
The sources disagree here, even within one organisation. In its food overview, the American Kennel Club says dogs can eat small amounts of tuna, cooked or canned in water. In its tuna article, however, the answer is no because of the high mercury content. The MSD Veterinary Manual explains the background: predatory fish at the top of the food chain accumulate high levels of mercury, and fish products have caused chronic poisoning in cats. Our approach between these positions: rarely, a little and never raw.
What to keep in mind
- Not regularly: Mercury accumulates. One bite is very different from a tin every week.
- Never raw: The AKC generally advises against raw fish because of parasites and germs.
- Only in water: Tuna in oil, with seasonings or salt is not a good choice.
- Cat food: If your dog likes eating from the cat’s bowl, check whether the food contains tuna.
What if your dog has eaten tuna?
According to the AKC, there is no need to worry if your dog has stolen a bite from your plate. A small amount does not cause mercury poisoning. If your dog eats tuna frequently and develops tremors, coordination problems, impaired vision, bloody vomit or bloody diarrhoea, take them to the vet and explain how often they have had tuna.
If you suspect poisoning, contact your vet or an emergency veterinary service immediately.
Our free feeding calculator shows you how much food your dog needs each day and how to account for snacks. You can find more on meal plans and treats in our book “Dog Nutrition and Meal Plans” (book in German), and our free Puppy Starter Pack helps you get ready for a puppy. To give your dog a place on your wall, explore our dog portraits from your own photo or choose an individual portrait.
Further reading
- How to calculate how much food your dog really needs
- Is my dog overweight? How to assess body condition and ideal weight
- Adding rice and potatoes to dog food: how to account for extras
Sources, accessed on 20.10.2026: American Kennel Club, Can Dogs Eat Tuna? and Human Foods Dogs Can and Can’t Eat (Tuna, Fish); MSD Veterinary Manual, Mercury Toxicosis in Animals.
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