Foods Toxic to Cats: Doses, Symptoms, and the First 30 Minutes

The foods that kill cats are not exotic. Onion and garlic cause red blood cell destruction at around 5 g per kg of body weight; a single leaf or the pollen from a true lily causes acute kidney failure; xylitol at 0.1 g/kg drops blood glucose within 30 minutes. Below is the list worth taping inside a kitchen cupboard, with the numbers that decide whether it is a phone call or an emergency.

The forbidden list, with doses

Food	Toxic dose for a cat	First signs	Onset
Onion, garlic, leek, chive	~5 g/kg onion; garlic more potent	Weakness, pale gums, dark urine	1–5 days
True lily (Lilium, Hemerocallis)	Any part, including pollen and vase water	Vomiting, drooling, then no urine	12–72 hours
Xylitol	0.1 g/kg for hypoglycaemia	Wobbling, collapse, seizures	30–60 minutes
Chocolate	20 mg/kg theobromine (mild)	Vomiting, racing heart, tremors	2–4 hours
Alcohol	5–8 ml/kg of pure ethanol	Staggering, low temperature, coma	30–90 minutes
Grapes and raisins	No established safe dose	Vomiting, then kidney injury	6–24 hours
Raw bread dough	A few spoonfuls	Bloated abdomen, drunken gait	30–60 minutes
Caffeine	~20 mg/kg	Restlessness, fast heart, tremors	1–2 hours

Lilies: the most lethal thing in a bouquet

True lilies — Easter, tiger, Asiatic, Japanese show — and daylilies cause acute tubular necrosis in cats. Every part is toxic: petals, leaves, stamens, pollen, and the water in the vase. A cat that walks past a bouquet, brushes the pollen onto its fur and grooms it can be in kidney failure 36 hours later, and the damage is often irreversible by the time the cat stops eating.

There is no safe quantity and no home treatment. If exposure is suspected, go immediately; aggressive fluid therapy started within 18 hours carries a much better prognosis than treatment started on day three. Lilies of the valley and peace lilies are a different mechanism — heart and irritation respectively — but also belong out of the house.

Onion, garlic, and the hidden powders

Alliums contain organosulphur compounds that oxidise feline haemoglobin into Heinz bodies. Cats are far more susceptible than dogs because their haemoglobin oxidises more readily. Around 5 g of onion per kg of body weight is enough to cause haemolytic anaemia; garlic is roughly five times more potent by weight, and onion powder is more concentrated than the raw vegetable.

The practical risk is not a cat eating an onion. It is onion powder in soup, stock, gravy, baby food, seasoned meat, and dog food. A few tablespoons of onion-rich broth is a real exposure for a 4 kg cat. Signs appear one to five days later — pale gums, weakness, dark urine — so the meal is long forgotten by the time the cat is ill.

Chocolate, caffeine, xylitol

Theobromine is the toxin in chocolate, and cats are more sensitive than dogs per kilogram. Mild signs from about 20 mg/kg, cardiac effects from 40–50 mg/kg, seizures above 60 mg/kg. Dark chocolate and cocoa powder are the dangerous forms: 10 g of dark chocolate can approach the mild-sign threshold for a small cat, while 10 g of milk chocolate usually cannot.

Xylitol is worse because the dose is tiny. At 0.1 g/kg it triggers an insulin surge and hypoglycaemia within 30 minutes; around 0.5 g/kg it can cause liver failure. Half a stick of sugar-free gum may hold 0.3 g — enough for a 3 kg cat. Xylitol is also in sugar-free peanut butter, some toothpastes and certain liquid medicines.

Raw fish, raw egg, milk

Raw fish contains thiaminase, which destroys vitamin B1; a cat fed raw fish several times a week can develop neurological signs in two to four weeks. Raw egg white contains avidin, which binds biotin. Cow's milk is not toxic but most adult cats are lactose intolerant, and 50 ml produces diarrhoea within hours.

Grapes, alcohol, dough, salt

Grapes and raisins cause acute kidney injury in dogs at low doses, and while feline cases are less well documented, no safe dose has been established and the advice is the same: treat any ingestion as an emergency. Ethanol at 5–8 ml/kg is life-threatening, and it hides in rum-soaked cake, liqueur chocolates, mouthwash, hand sanitiser. Raw bread dough both expands in the stomach and ferments into ethanol, so a few spoonfuls is a double exposure.

Salt deserves a line of its own: a teaspoon of salt in a small cat is enough to cause sodium poisoning — vomiting, tremors, seizures. Never induce vomiting with salt water, a folk remedy that has killed cats.

The first 30 minutes

1. Do not induce vomiting unless a vet tells you to. It is wrong for caustics, sharp bones and an already-dull cat.
2. Record the food, the amount and the time. "A bit of onion soup" cannot be dosed; "two tablespoons at 19:40" can.
3. Keep the packaging. The ingredient list may settle whether xylitol or onion powder was present.
4. Call the vet or a poison line and say the weight of the cat and the calculated mg/kg if you can.
5. Do not give milk, oil, or salt water. None of them help and two of them cause new problems.

Not food, but in the same cupboard

Paracetamol is lethal to cats at around 10 mg/kg — one tablet can kill an adult cat — and ibuprofen causes kidney injury at 50 mg/kg. Tea tree, eucalyptus, citrus and peppermint essential oils are toxic by contact and by diffusion; a diffuser in a closed room is an exposure. Bleach and drain cleaner cause chemical burns, and the response is water, not vomiting.

If you are unsure whether something is dangerous, assume it is and call. The cost of a phone call is zero, and the cost of waiting until morning is often a cat in acute kidney failure. Our health section covers the clinical side, and the food guides cover what is safe to feed instead.

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