Why?
Tuna is a large predatory fish that builds up mercury over its life, so cats that eat a lot of it are more exposed. A tuna-heavy diet can also lead to vitamin E deficiency, because its unsaturated fats raise the need for that vitamin. Its strong taste is another issue: some cats get hooked and start snubbing their regular food. Tuna for people isn't a complete food, unlike tuna cat foods formulated to be balanced.
How much?
About a teaspoon of tuna packed in water, ideally with no added salt, once a week at most. Drain it well and skip tuna in oil or brine. Fresh tuna should be cooked.
The risks
- Mercury buildup if fed often
- Vitamin E deficiency on a tuna-heavy diet
- Addiction: your cat may refuse regular food
- Tuna in oil or brine: diarrhea, excess salt
- Raw tuna: parasites and bacteria
Your cat ate some: what now?
A can of tuna swiped from the counter isn't an emergency: mercury is a problem with frequent feeding, not a single meal. Watch for 24 to 48 hours and call your vet for repeated vomiting or heavy diarrhea. If it was tuna in oil, expect soft stools.
Better options
Mix it up with a bite of plain cooked chicken or salmon, or half a sardine packed in water with no added salt.
Common questions
Can kittens eat tuna?
It's best to be cautious. Kittens need food made for growth, and getting hooked on tuna early can turn them into picky eaters. A tiny taste now and then won't hurt, but nothing more.
Can cats drink tuna water?
The water from tuna packed in water with no added salt is fine in small amounts and can encourage drinking. Skip the oil and brine, which are too fatty or salty.
This information is general and does not replace advice from a veterinarian. If your cat has swallowed something toxic, call your vet or an animal poison control center right away, without waiting for symptoms.