Can Cats Eat Tuna?

Why Cats Love Tuna

Open a can of tuna anywhere in the house and your cat will appear. The attraction is biological: tuna has an unusually potent scent profile, driven by amino acids and volatile compounds that light up feline olfactory receptors. That reliable appeal is exactly why so many commercial cat treats are tuna-flavored.

Palatability, though, is not the same as nutritional suitability. A cat's enthusiasm for tuna says nothing about whether it's safe in large or frequent amounts — people crave food that isn't good for them daily, too.

Health Risks of Too Much Tuna

Mercury Accumulation

Tuna is a large, predatory ocean fish that sits near the top of the marine food chain. As smaller fish accumulate methylmercury from their environment, that mercury concentrates further up the chain — a process called bioaccumulation. Species like bluefin, yellowfin, and bigeye tuna carry the highest mercury loads.

For context, cats typically weigh only 4–6 kg (9–13 lb). Even low-level chronic mercury exposure that might be manageable for a larger animal can accumulate to toxic levels in a cat over time. Signs of mercury toxicity include loss of coordination, muscle tremors, and visual disturbances — symptoms that can be subtle in early stages and are often mistaken for other conditions.

Yellow Fat Disease (Steatitis)

Steatitis is one of the more serious risks of a tuna-heavy diet, and one many owners have never heard of. Tuna is high in polyunsaturated fatty acids, and fed in large quantities over time these fats deplete the body's reserves of vitamin E. The result is steatitis, an inflammatory condition in which the cat's fat deposits become hard, painful, and inflamed.

Steatitis is notoriously painful. Affected cats often cry out or bite when touched along their sides or abdomen, develop fever, become lethargic, and lose their appetite. Cases were historically documented in cats fed primarily fish-based diets — particularly tuna — before the connection was understood.

High Sodium in Canned Tuna

Human-grade canned tuna is made for people, which means plenty of added salt. A serving of canned tuna in water typically contains 150–400 mg of sodium, depending on the brand. Cats need very little sodium — the minimum requirement for an average adult is around 42 mg a day, and the published safe upper limit is roughly 740 mg a day — so a single serving takes up a large share of that range.

Chronic sodium excess puts sustained strain on the kidneys and cardiovascular system — a particular concern for cats with pre-existing kidney disease, which is very common in older cats.

Tuna Preference

The behavioral risk is easy to underestimate. Cats can develop an intense, fixed preference for tuna's flavor and texture, to the point of refusing all other foods. That creates a difficult cycle: the owner feeds more tuna because the cat won't eat anything else, and the preference deepens further.

A cat subsisting mainly on tuna will develop serious nutritional deficiencies over time, missing adequate taurine, calcium, fat-soluble vitamins, and other nutrients a complete cat food supplies.

How to Feed Tuna Safely

VCA's own guidance goes further and advises against offering tuna at all, even as a treat, because it lacks essential nutrients and is high in unsaturated fat. If you decide to offer it anyway, keep to these limits:

• Choose water-packed, no-salt-added tuna: Avoid oil-packed varieties (high in fat) and any tuna with added salt, flavorings, or seasonings.
• Keep portions small: A reasonable serving is roughly 1 teaspoon (about 5g) per treat session.
• Limit frequency: No more than 1–2 times per week at most. Many vets suggest less frequent than that.
• Never as a meal replacement: Tuna lacks the complete nutritional profile cats require. It should supplement, never replace, a complete and balanced cat food.
• Prefer smaller tuna species: Skipjack and light tuna have lower mercury concentrations than albacore, yellowfin, or bluefin. When choosing canned tuna, "light tuna" typically means skipjack.
• Cat-specific tuna treats: Commercially produced cat treats with tuna flavoring are formulated with appropriate sodium levels and supplementation — a safer option than human canned tuna.

Signs of Tuna-Related Problems

Watch for these warning signs, especially if your cat has been eating tuna regularly:

• Reduced appetite for regular food — may indicate developing tuna preference fixation
• Lethargy, stiffness, or pain when touched along the sides — potential steatitis
• Wobbling, incoordination, or tremors — potential mercury toxicity
• Fever combined with loss of appetite — possible yellow fat disease

If you observe any of these signs, contact your veterinarian promptly. Be sure to mention your cat's dietary history, including how often tuna has been offered.