Can dogs eat tuna every day?

No, this is exactly the pattern to avoid. Mercury from tuna builds up with repeated feeding, so a small amount given daily is a bigger concern than the same amount given occasionally. Keep tuna to an infrequent treat rather than a regular addition to your dog's meals.

Is tinned tuna safe for dogs?

In small, occasional amounts, tuna packed in spring water and well drained is the least risky option. Tuna in brine adds unnecessary salt, and tuna in oil adds unnecessary fat, so spring water is the better choice of the three if you are giving your dog a small piece.

Can puppies eat tuna?

It's best avoided. Puppies are smaller and more affected by both the mercury and salt content of tuna than adult dogs, and their diet should already be complete and balanced for growth without needing any addition of tuna at all.

What are the signs of too much salt from tuna?

Watch for vomiting, diarrhoea, unusual thirst or lethargy after a dog has eaten a significant amount of tinned tuna. In a serious case this can progress to salt poisoning, which needs urgent veterinary attention, so ring your vet rather than waiting if your dog has raided an open tin.

Is fresh tuna safer than tinned for dogs?

Fresh, plainly cooked tuna with nothing added avoids the extra salt that comes with tinned brine or the extra fat that comes with tinned oil, so it is a slightly better option if you have it available. The mercury consideration applies to fresh and tinned tuna equally, so the same small, occasional amounts still apply.

Is tuna bad for dogs?

Tuna is not toxic to dogs, but it is not a food to give regularly either. A small amount of plain tuna in spring water, given occasionally, is unlikely to cause harm — the concerns are mercury building up with repeated feeding and the salt content of tinned tuna, both of which make 'occasional' the important word rather than 'safe' on its own.

Why tuna is a 'sometimes' food, not a safe one

Tuna is a predatory fish, which means it accumulates more mercury over its lifetime than smaller fish lower down the food chain. A single small piece is not a meaningful dose for most dogs, but tuna given often, over weeks and months, is where the concern genuinely lies — the risk builds with repetition, not with one serving.

Tinned tuna also tends to carry more salt than fresh, especially if it is packed in brine, and tuna in oil adds unnecessary fat on top of that. Neither makes an occasional small amount dangerous, but neither makes tuna the treat to reach for regularly either, and there is no meaningful nutritional gap in a complete dog food that tuna needs to fill.

If you do give it, do it this way

Choose tuna packed in spring water rather than brine or oil, and drain it well before offering a small piece to your dog. Fresh, plainly cooked tuna with no seasoning is a better option than tinned if you have it available, since you control exactly what has been added.

Keep portions genuinely small and infrequent — a few flakes now and then, not a regular addition to meals — and avoid it altogether for puppies, smaller dogs and any dog on a restricted-salt diet, since they are more affected by both the mercury and the sodium for their size. Larger, active adult dogs have more scope to tolerate an occasional small amount than a toy breed of the same age.

Signs something has gone too far

Excess salt from a large amount of tinned tuna can cause vomiting, diarrhoea, unusual thirst or lethargy, and in a serious case can lead to salt poisoning, which is a genuine emergency. This is more of a risk from a dog raiding an open tin than from the small amounts described above.

If your dog has eaten a significant amount of tuna, especially packed in brine, or is showing any of those signs, ring your vet rather than waiting to see whether it settles on its own.

Safer things to give instead

Things we stock that owners commonly reach for here. Nothing on this page depends on you buying one.

Chicken-Wrapped Milk Stick Dog Treats

Chewy dog treats of soft milk sticks wrapped in real chicken for tasty, protein-rich rewarding.

From£12.99

Turkey Tail Mushroom & Probiotic Powder

A bacon-flavoured turkey tail mushroom and probiotic powder you sprinkle over food. Made to support immunity, energy and gut health, with scoop guidance for every weight from small to large pets.

£13.99

Yeast Protection Gut & Skin Supplement For Dogs

A powdered daily supplement for dogs to support normal gut flora and healthy skin, with a measuring scoop.

£14.99

Browse all of Dogs →

Common questions

Can dogs eat tuna every day?: No, this is exactly the pattern to avoid. Mercury from tuna builds up with repeated feeding, so a small amount given daily is a bigger concern than the same amount given occasionally. Keep tuna to an infrequent treat rather than a regular addition to your dog's meals.
Is tinned tuna safe for dogs?: In small, occasional amounts, tuna packed in spring water and well drained is the least risky option. Tuna in brine adds unnecessary salt, and tuna in oil adds unnecessary fat, so spring water is the better choice of the three if you are giving your dog a small piece.
Can puppies eat tuna?: It's best avoided. Puppies are smaller and more affected by both the mercury and salt content of tuna than adult dogs, and their diet should already be complete and balanced for growth without needing any addition of tuna at all.
What are the signs of too much salt from tuna?: Watch for vomiting, diarrhoea, unusual thirst or lethargy after a dog has eaten a significant amount of tinned tuna. In a serious case this can progress to salt poisoning, which needs urgent veterinary attention, so ring your vet rather than waiting if your dog has raided an open tin.
Is fresh tuna safer than tinned for dogs?: Fresh, plainly cooked tuna with nothing added avoids the extra salt that comes with tinned brine or the extra fat that comes with tinned oil, so it is a slightly better option if you have it available. The mercury consideration applies to fresh and tinned tuna equally, so the same small, occasional amounts still apply.

Sources

Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.

Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.