Can Cats Eat Onions? No: Toxic Dose, Symptoms & What to Do

Toxic

No, onions are toxic to cats

Onions are toxic to cats, and cats are more sensitive than dogs. They damage red blood cells and can cause anemia. Per the Merck Veterinary Manual, less than a teaspoon of cooked onion or about 5 g/kg of raw onion can affect a cat.

If your cat ate onions: call your vet or animal poison control now: ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661. Do not make your cat vomit unless a vet tells you to.

Onions for cats at a glance

Can cats eat it?	Toxic
Calories	Not recommended as a treat
Main benefit	None for pets
Main risk	Damage red blood cells (Heinz body anemia)
Kittens?	No

How much onion is dangerous?

The Merck Veterinary Manual notes cats can be affected by about 5 g/kg of raw onion, or less than a teaspoon of cooked onion. The table shows the amount of fresh onion reaching the 5 g/kg level. Powdered onion is far more concentrated.

Cat weight	Fresh onion at threshold	Roughly
6 lb	13.6 g	≈ 12.4% of a medium onion
8 lb	18.1 g	≈ 16.5% of a medium onion
10 lb	22.7 g	≈ 20.6% of a medium onion
12 lb	27.2 g	≈ 24.7% of a medium onion
14 lb	31.8 g	≈ 28.9% of a medium onion

Smaller amounts are not "safe": effects build up over several days of exposure, and individual sensitivity varies.

Symptoms to watch for

Vomiting and drooling
Lethargy and weakness
Pale gums
Fast breathing and dark urine (often delayed days)

Why it is dangerous

Risks

Damage red blood cells (Heinz body anemia)
Cats are more susceptible than dogs
Onion powder in baby food, broth and gravy is a common hidden source

How to keep your cat safe

Never feed onions, leeks, chives or shallots
Check broths and baby food labels before sharing
Call your vet after any ingestion

What to do if your cat ate onions

Work out how much was eaten, when, and your cat's weight. Keep any packaging.
Call your vet or animal poison control now: ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661.
Do not make your cat vomit unless a vet tells you to (hydrogen peroxide is not safe for cats).
Follow your vet's advice even if your cat seems fine: treatment works best before signs start.

Safer treats to give instead

These are safe for cats in treat-size amounts:

Check your cat's full daily needs with the cat food calculator.

Onions and cats: FAQ

Can cats have onions?

No. Onions are toxic to cats, and cats are more sensitive than dogs. They damage red blood cells and can cause anemia. Per the Merck Veterinary Manual, less than a teaspoon of cooked onion or about 5 g/kg of raw onion can affect a cat.

Is a small amount of onion okay for cats?

No. Cats can be affected by very small amounts, and repeated exposure adds up.

Can cats eat food cooked with onion?

No. Gravy, soup and leftovers with onion are a common cause of poisoning.

How is onion toxicity treated?

Treatment may include inducing vomiting, activated charcoal, fluids, and in severe cases a blood transfusion.

Can kittens eat onions?

No. Kittens are smaller and more vulnerable than adults, so the risks are greater. Call your vet if your kitten ate any.

More "can cats eat" guides

Browse lists: all vegetables cats can eat · human foods cats can eat · foods cats can't eat

Sources

This guide is general information for healthy adult cats. Cats with medical conditions (such as diabetes, pancreatitis, kidney disease or food allergies) may need different advice from their vet.

Can Cats Eat Onions?