Occasional plain tinned tuna in spring water (not brine or oil) is usually safe as a treat. Tuna should not replace complete cat food — daily feeding causes nutritional problems.

Can cats eat tinned tuna every day?

No — daily tuna lacks essential nutrients cats need and can cause mercury accumulation and 'tuna addiction' where cats refuse balanced food.

Can kittens eat tuna?

Kittens need complete kitten food for growth. Plain tuna alone does not provide balanced nutrition — ask your vet before offering any human food to kittens.

Is tuna in brine or oil safe for cats?

Avoid brine (high salt) and oil (high fat). Choose plain tuna in spring water with no added salt — drain well and offer small amounts only.

Cat Health

Can Cats Eat Tuna UK? Tinned, Fresh & Daily Feeding Risks

Published 25 June 2026Last updated 25 June 20262 min read

Quick answer

Occasional plain tinned tuna in spring water is usually fine as a treat. Do not feed tuna daily — it is not nutritionally complete, can cause mercury build-up over time, and some cats become fixated and refuse proper cat food.

Can cats eat tinned tuna?

According to the PDSA and Blue Cross, a small amount of plain tinned tuna in spring water — drained, with no added salt — can be an occasional treat for most healthy adult cats.

Tuna is not a balanced meal. Complete wet or dry cat food provides taurine, vitamins, and minerals that tuna alone lacks.

Tuna in brine or oil — avoid

Product	Problem
Tuna in brine	High salt — harmful to cats
Tuna in sunflower or olive oil	Excess fat — digestive upset
Flavoured tuna	Onion, garlic, spices — toxic
Human tuna sandwiches	Mayonnaise, onion, bread — unsuitable

Why daily tuna is a problem

Nutritional imbalance

Cats need taurine, calcium, and balanced vitamins from complete cat food. Feeding mostly tuna can contribute to serious deficiency over time.

Mercury

Large predatory fish accumulate mercury. Occasional small amounts are unlikely to harm healthy cats; regular daily feeding increases long-term risk — especially in kittens and pregnant queens.

Tuna addiction

Some cats develop a strong preference for tuna and refuse their normal diet. This makes balanced feeding difficult and can lead to weight loss or deficiency.

Fresh tuna

Plain cooked fresh tuna without seasoning can be offered in small amounts — same rules as tinned: occasional only, not a staple.

Never feed raw fish regularly without veterinary nutrition advice — thiaminase in some raw fish can affect vitamin B1 if fed in large amounts over time.

When to see your vet

Book a check if your cat:

Refuses all cat food and only wants tuna
Loses weight while eating human food
Vomits or has diarrhoea after tuna
Is a kitten, pregnant, or has kidney disease — dietary restrictions may apply

Sources & further reading

Facts in this guide are rewritten in plain English from publicly available UK advice. We name the organisation where a specific point comes from their guidance. Links below go to the original pages — use them to read the source material directly.

PETHEALTH+ is independent. These organisations do not sponsor, approve, or partner with this website. Guidance checked against sources listed below (last updated 2026-06-25).

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Frequently Asked Questions

Can cats eat tuna?: Occasional plain tinned tuna in spring water (not brine or oil) is usually safe as a treat. Tuna should not replace complete cat food — daily feeding causes nutritional problems.
Can cats eat tinned tuna every day?: No — daily tuna lacks essential nutrients cats need and can cause mercury accumulation and 'tuna addiction' where cats refuse balanced food.
Can kittens eat tuna?: Kittens need complete kitten food for growth. Plain tuna alone does not provide balanced nutrition — ask your vet before offering any human food to kittens.
Is tuna in brine or oil safe for cats?: Avoid brine (high salt) and oil (high fat). Choose plain tuna in spring water with no added salt — drain well and offer small amounts only.