What food is bad for cats?

Cats are curious by nature. And their curiosity often leads them to whatever their owners are eating.

But a cat’s digestive system works differently to ours. Some foods that seem harmless can cause stomach upset and even toxic reactions. And that can result in an emergency visit to the vet and a claim on your pet insurance.

Here, we explain which foods are safe for cats, which aren’t, and which ones are only suitable in small amounts. It’s based on the latest research from Mars Petcare* and the Waltham Petcare Science Institute*.

Research from Mars Petcare* highlights how your cat’s body is unique. From their digestive system to their teeth to how they taste.

The differences in a cat's biology explain why human foods can make them very unwell, very quickly. And why many emergency pet insurance claims relate to the sudden ingestion of dangerous foods.

For Tesco Pet Insurance claims relating to cats eating toxic foods, the average payout is £794.65**. So the cost of treating your cat could be expensive without insurance.

No. Chocolate is toxic to cats.

It contains theobromine and caffeine. These can cause agitation, excitability, tremors, convulsions and heart problems. Even a small bite can be fatal. And dark chocolate is the most dangerous.

There are a few cat-safe vegetables, listed below. But you should only give these to your cat as a treat. Cats are meat-eaters and won’t get the nutrients they need from plant-based foods.

These vegetables can be safe for cats in small amounts, if they’re properly prepared. That means plain, cooked, and with no seasoning.

The following vegetables are toxic to cats, even when cooked. They can cause haemolytic anaemia, which is a serious blood disorder.

These vegetables are also unsafe for cats to eat.

Are onions poisonous to cats?

Yes. Onions are toxic to cats, cooked or raw. And should always be avoided.

Is garlic poisonous to cats?

Yes. Garlic is more dangerous than onions and extremely toxic to cats. It causes damage to a cat’s red blood cells.

These fruits are safe for cats, but only in tiny amounts.

The following fruits pose a toxic and/or choking hazard to your cat and should always be avoided.

Are grapes safe for cats?

No. Grapes are highly dangerous and must never be given to cats or dogs. Even one grape can cause vomiting, lethargy and severe kidney failure.

Can cats eat raisins?

No. Raisins are toxic to cats and dogs and can cause sudden kidney failure.

Dried grapes, such as sultanas and currants, are also toxic to cats and dogs.

Yes. Cats shouldn’t be fed dog food for their meals. It doesn’t contain the nutrients they need and could lead to long-term health problems.

Cats need higher levels of:

Dog food doesn’t meet these requirements.

Generally, no. Milk and dairy can cause vomiting and diarrhoea in cats.

We’re all familiar with the image of a cat with a saucer of milk, but most adult cats are actually lactose intolerant. And the idea simply comes from a mixture of tradition, old farming practices, and pop culture imagery.

Kittens do produce lactase - the enzyme that breaks down lactose - because they need it to digest their mother’s milk. But once they’re weaned, their lactase production drops sharply. And by then, milk has become increasingly unsafe for them.

Generally, no. These can all cause digestive upset.

Most cats are lactose intolerant, so cow’s milk and goat’s milk commonly cause vomiting and diarrhoea.

If you want to give your cat milk, choose a lactose free cat specific milk.

Pet stores sell lactose-free milk formulated specifically for cats. And it’s generally safe as an occasional treat.

It’s not just fruit and veg, chocolate and milk you need to watch out for. These foods can also be dangerous for cats.

A cat’s curiosity could get it into trouble if it comes across these things. So always keep them out of reach.

If you also have a dog, many of the same rules around human foods apply. You can learn more in our guide - What food is bad for dogs?

“Certain foods are common causes of intoxications (poisonings) in pets, and fatalities can occur... Be aware that a number of household and garden plants are also toxic and are especially a problem for inquisitive puppies and kittens.

Generally, prognosis is much improved when early treatment is initiated. And the vet is informed of what, when and how much of a food item or plant is ingested.”

Prof Anne Marie Bakke (DVM, PhD Nutrition)
Global Nutrition Technical Advisor
Waltham Petcare Science Institute

Acting calmly and quickly gives your cat the best chance of a full recovery.

Cats can be fun and mischievous. But owning a pet is a big responsibility. And they can take a lot more looking after than you might realise.

For more advice about looking after a cat, take a look at our guide - Looking after cats.

If your cat eats something they shouldn’t, it can lead to expensive treatment and unexpected vet bills.

Tesco Pet Insurance can help to protect both your pet and your pocket, with:

With Tesco Pet Insurance, you can choose from 3 different types of cover:

You can save money on all our Pet Insurance policies with your Clubcard. And if you insure more than one pet with us, you’ll get a multi pet discount on each policy.

You can learn about the importance of pet insurance in our guide - Why is pet insurance important?

Tesco Pet Insurance is arranged, administered and underwritten by Pinnacle Insurance Ltd.

vetfone is provided by Vetsdirect Ltd.

You'll find complete details of the cover, monetary limits, exclusions, excesses and terms in our policy documents.

*Mars Science & Diagnostics - A Better World For Pets, 2025.

*Waltham Petcare Science Institute

**Tesco Pet Insurance claims payment data, January 2025-February 2026. Provided by Pinnacle Insurance Ltd.