Foods Last reviewed: 2026-10-27

Onions, garlic, leeks and chives (Allium) in Pets

Onion and garlic can cause anaemia in dogs and cats days after eating. Compare grams eaten per kg with Merck's 15–30 g/kg (dogs) and 5 g/kg (cats) figures.

At a glance
Which animals Cats are more sensitive than dogs.
Signs and timing Vomiting, diarrhoea, drooling and stomach pain can occur within a day.
What to do now Call your vet or a poison line with your pet's weight and an estimate of the onion or garlic eaten, including whether it was raw, cooked or powdered.

What It Is

Plants in the Allium family contain sulphur compounds (such as n-propyl disulphide and thiosulphates) that damage haemoglobin in red blood cells. Damaged cells form Heinz bodies and are destroyed, causing anaemia. Garlic is generally considered several times more potent than onion by weight.

Where Pets Come Across It

Leftovers such as stews, gravy, pizza and stir-fries; onion and garlic powder in seasonings, stock cubes and some baby foods; and raw onions in the vegetable rack. Cooking does not remove the toxin, and dried powders are concentrated.

Which Animals Are Affected

Cats are more sensitive than dogs. Japanese dog breeds such as the Akita and Shiba Inu may be more susceptible. Horses, cattle and sheep can also be affected by grazing wild onions.

Published Toxic Dose

The Merck Veterinary Manual reports clinical signs in dogs after 15–30 g of raw onion per kg of body weight, and in cats after about 5 g/kg of raw onion or less than a teaspoon of cooked onion. Smaller amounts eaten over several days can add up. Note the unit: these thresholds are grams of onion, not milligrams of a toxin.

Onions, garlic, leeks and chives (Allium) Dose Exposure Calculator
Enter your pet's weight and estimated quantity missing to compare against veterinary literature thresholds.
1 clove garlic ≈ 5g; 1 medium onion ≈ 150g.
Calculating...

Signs and How Soon They Appear

Vomiting, diarrhoea, drooling and stomach pain can occur within a day. Signs of anaemia usually appear 1 to 5 days later: tiredness, pale gums, fast breathing, a fast heart rate, and red-brown urine.

What to Do Right Now

Call your vet or a poison line with your pet's weight and an estimate of the onion or garlic eaten, including whether it was raw, cooked or powdered. Your vet may want a blood test a few days later even if your pet seems fine. Do not induce vomiting at home.

Frequently Asked Questions

Is cooked onion safe for dogs?
No. Cooking, drying and powdering do not destroy the compounds that damage red blood cells.
When does onion anaemia appear?
Usually 1 to 5 days after eating, which is why a follow-up blood test is often advised.

Sources and References

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