Can Dogs Eat Tuna? Mercury and Safe Amounts

By Tailwisp Editorial TeamUpdated October 17, 20263 min read

Tuna is a pantry staple and an irresistible smell for many dogs. A small taste is unlikely to hurt, but tuna sits near the top of the food chain, which means it accumulates mercury. That is why it should be an occasional treat.

Nutrition

Tuna offers lean protein, omega-3 fatty acids, selenium and B vitamins. These are useful nutrients, but a dog on a complete diet does not need extra. See fat and omega fatty acids.

The mercury issue

Mercury is a heavy metal that builds up in fish, particularly large predatory species such as tuna. Chronic exposure can damage the nervous system and kidneys. Dogs are smaller than people, so the same portion represents more mercury per kilogram of body weight. Occasional small amounts are low risk, but regular tuna meals are not a good idea.

Types of tuna

• Skipjack and light tuna are generally lower in mercury.
• Albacore (white) tuna is higher.
• Bigeye and bluefin are highest.

Variety also matters. If you feed fish, rotating species and using smaller fish such as sardines in water can reduce risk. See salmon for dogs.

Canned tuna choices

• In water, no added salt. Best for dogs.
• In oil. High in fat, which can upset the stomach or contribute to pancreatitis. If you use it, drain thoroughly.
• With flavorings, such as garlic, onion, spices or sauces. Avoid. See onions and garlic.
• High-sodium varieties. Avoid. See salt poisoning in dogs.

Raw tuna and sushi

Raw fish can carry parasites and bacteria, and sushi may include rice vinegar, wasabi, soy sauce and other seasonings. Cook tuna fully if you serve fresh fish, and do not share sushi.

How much?

Treats should be no more than about ten percent of daily calories. As a rough guide, one or two teaspoons suits a small dog, and a tablespoon a large dog, no more than occasionally. If your dog eats tuna regularly, or has eaten a lot, mention it to your vet.

Ways to use it

• Mix a little drained tuna into kibble for a picky eater.
• Use a small dab to hide a pill.
• Stuff a lick mat or toy, then freeze.

Tuna and pets with conditions

• Pancreatitis and obesity: Avoid oily tuna. See diet for pancreatitis.
• Kidney disease: Mercury and salt are concerns. Ask your vet.
• Allergies: Fish allergy is uncommon but possible.

Signs of mercury problems

These are rare, but they include tremors, loss of coordination, behavior changes and kidney problems. If you suspect heavy exposure, contact your vet.

Better fish options

Sardines packed in water are a smaller, lower-mercury fish. Cooked salmon is also popular. Both should be served plain and in small portions.

Tuna and thiamine

Raw fish can contain enzymes that destroy thiamine, a B vitamin, and dogs fed large amounts of raw fish for long periods may develop deficiency. Cooked or canned tuna does not carry that particular risk, since heat inactivates the enzyme. It is another reason why a varied diet with a complete food as the base is safer than relying on any single ingredient.

Cats and tuna

If you share your home with a cat, watch that your dog does not eat the cat's tuna-flavored food regularly, which is often richer and not formulated for dogs. Cat food is higher in protein and fat and can upset a dog's stomach or contribute to weight gain. Feed pets separately, and store cat food out of reach.

The takeaway

Tuna is fine occasionally in small amounts. Choose plain, water-packed light tuna and keep it a treat.

This article is general educational information, not veterinary advice. Every dog is different. If your dog is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.