Are onion and garlic toxic to cats?
Yes. Onion, garlic, leek, shallot and chives damage a cat's red blood cells, whether raw, cooked, dried or powdered, and cats are the most sensitive species. Around 5 g of onion per kg of body weight has caused poisoning in cats, about 20 g for a 4 kg cat, and garlic is three to five times stronger. The anaemia builds over several days, so call your vet today with the amount, even if your cat seems fine.
General information, not veterinary advice. If your pet may have eaten this, contact a vet now; do not wait for signs.
What to do right now
- Remove any remaining food and keep the packet or recipe
- Estimate how much onion or garlic your cat ate, including powder in sauces or gravy
- Weigh your cat or use the last known weight
- Call your vet today with the amount and weight
- Do not try to make your cat sick at home
Go to an emergency clinic now if
- Pale, white or yellow gums
- Fast breathing or breathlessness at rest
- Weakness, collapse or reluctance to move
- Red or brown urine
- A large amount was eaten, especially garlic, onion powder or dried onion
Who to call
Your own vet first. If they are closed, the nearest emergency or out-of-hours clinic.
In the United States
Both answer 24 hours a day and may charge a consultation fee.
Signs to watch for
| Sign | Usually starts |
|---|---|
| Vomiting, diarrhoea, drooling | 6-24 hours |
| Reduced appetite, tummy pain | 6-24 hours |
| Lethargy, weakness | 1-5 days |
| Pale or yellow gums | 1-5 days |
| Fast breathing, fast heart rate | 1-5 days |
| Red or brown urine | 3-5 days |
Why are onion and garlic toxic to cats?
Onions, garlic, leeks, shallots and chives belong to the Allium family. They contain sulphur compounds that damage haemoglobin, the oxygen-carrying protein inside red blood cells. Damaged haemoglobin clumps into small lumps called Heinz bodies, and the body destroys the affected cells, causing haemolytic anaemia. The Merck Veterinary Manual names cats as the most susceptible species, ahead of dogs.
How much onion or garlic is dangerous for a cat?
The Merck Veterinary Manual reports poisoning in cats after about 5 g of raw onion per kg of body weight. Garlic is three to five times more toxic than onion, and dried or powdered forms are far more concentrated than fresh. For an average 4 kg cat that works out roughly as follows:
| What was eaten | Approximate amount that can harm a 4 kg cat |
|---|---|
| Raw or cooked onion | about 20 g, a couple of tablespoons chopped |
| Fresh garlic | about 4-7 g |
| Onion or garlic powder, dried flakes, soup mix | much less; call your vet with any amount |
These are estimates from limited data, not safe limits. Small amounts eaten on several days in a row can add up, which is why Pativo treats onion and garlic as dose-dependent and asks for the amount.
Why do signs take days to appear?
The damage to red blood cells starts within 24 hours and peaks at around three days, but a cat only looks ill once enough cells have been destroyed. PDSA notes that stomach signs usually appear 6 to 24 hours after eating, while signs of anaemia usually appear within one to five days. A cat that looks well the morning after is not out of danger, so watch the colour of the gums and the breathing for the rest of the week.
What will the vet do?
If your cat ate the onion or garlic within the last few hours, the vet may make it vomit with an injection and give activated charcoal. The vet will usually check a blood sample for anaemia and Heinz bodies, and may repeat it over the following days. Cats with significant anaemia may need fluids, oxygen and, in severe cases, a blood transfusion. PDSA reports that most cats recover fully.
How do I stop it happening again?
Do not share leftovers made with onion or garlic, such as gravy, stews, pizza, stuffing or takeaways, and check labels on human foods before offering them. Keep chopping boards and bins out of reach. If your cat stops eating or seems unwell in the days after, a symptom check can help you decide how soon to see the vet. Dogs are affected too: see onion and garlic in dogs.
Questions owners ask
Is baby food safe for a sick cat?
Check the label first. Some meat baby foods contain onion or garlic powder, which can harm a cat, especially if fed for several days.
Does cooking make onion safe for cats?
No. Raw, cooked, dried and powdered onion and garlic are all toxic. Concentrated forms such as powder, flakes and soup mixes are the most dangerous.
Is a small amount of garlic good for cats?
No. Garlic is three to five times more toxic than onion, and cats are the most sensitive species. Do not give garlic supplements unless your vet has advised it.
Sources
- Merck Veterinary Manual: Garlic and Onion (Allium spp) Toxicosis in Animals
- PDSA: Onion and Garlic Poisoning in Cats
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