Meats & proteins
Can cats eat tuna?
An occasional bite is fine, but a tuna habit brings mercury, sodium and nutritional imbalance.
Portion: About 1 teaspoon, occasionally. Never as a daily meal.
The short answer
A little tuna is fine as a rare treat, but it shouldn't become a habit. Human tuna isn't nutritionally complete for cats. Diets heavy in tuna have been linked to vitamin E deficiency (steatitis, or 'yellow fat disease'). It can also carry mercury, and many cats get so hooked they refuse their normal food. Choose tuna canned in spring water with no added salt, and never feed tuna in oil, brine or with seasonings.
Why the verdict
Tuna is a predatory fish that accumulates methylmercury. Fish rich in polyunsaturated fats can deplete vitamin E when fed heavily, causing painful inflammation of body fat (steatitis). Raw fish contains thiaminase, an enzyme that destroys vitamin B1; cooking and canning inactivate it. Brine and oil add sodium and fat, and the strong flavour can make cats fussy eaters.
How to prepare it
- Choose tuna in spring water, no salt added.
- Drain well. Never feed tuna in oil or brine.
- No mayonnaise, onion or seasoning (tuna salad is off-limits).
- Keep it to a teaspoon, no more than about once a week.
- Cat foods labelled 'complete' that contain tuna are fine as main meals.
Signs of trouble
- Vomiting or diarrhoea
- Refusing regular food (tuna 'addiction')
- Long-term overfeeding: pain when touched, reluctance to move, fever (steatitis)
- Wobbliness or tremors (very rare mercury toxicity)
Tuna & cats: FAQ
Is canned tuna bad for cats?
Occasional small amounts of tuna in water are fine. Regular feeding risks mercury exposure, nutrient imbalance and picky eating.
Can cats eat raw tuna?
Not recommended. Raw fish can carry parasites and bacteria and contains thiaminase, which breaks down vitamin B1.
Can cats drink tuna water?
A splash of water from tuna canned in spring water, with no salt, is fine as a topper. Avoid brine, which is very salty.
Related foods
See every food that’s toxic to cats →
Sources
- Cornell Feline Health Center — Feeding Your Cat (accessed 2026-09-29)
- Merck Veterinary Manual — Nutritional Requirements and Related Diseases of Small Animals (accessed 2026-09-29)
Last updated 2026-09-29. We are not veterinarians: this guide summarises published veterinary references and is not a substitute for advice from your vet. See our methodology and disclaimer.