Why?
Onion, like all alliums, contains sulfur compounds (including propyl disulfide) that oxidize the hemoglobin in red blood cells. The cells weaken, form Heinz bodies and are destroyed, which is called hemolytic anemia. Cats are especially sensitive, more so than dogs, and cooking, drying or powdering doesn't remove the toxicity. The damage can also add up if a cat eats small amounts often.
How much?
No amount is safe. Watch for hidden sources: sauces, soups, broths, gravy, ready meals, quiche, pizza, and even some meat-based baby foods, which often contain onion powder.
The risks
- Hemolytic anemia (destruction of red blood cells)
- Pale gums, weakness, fatigue, rapid breathing
- Dark, red or brown urine
- Vomiting, diarrhea, loss of appetite
- Symptoms that can be delayed by several days
Your cat ate some: what now?
Call your vet or an animal poison control center right away, without waiting for symptoms: anemia can take several days to appear. Don't make your cat vomit yourself. Note what it ate, how much and when, as that will help your vet.
Better options
A piece of plain cooked chicken or fish is a treat on its own, no seasoning needed. If you cook for your cat, set its portion aside before adding onion or garlic.
Common questions
Is onion powder bad for cats?
Yes, and it's even more concentrated than fresh onion. Check labels on broths, seasoned meats and baby food before sharing anything.
Can cats eat gravy or broth made with onion?
No. The toxic compounds pass into the liquid, so gravy, broth and soup made with onion are just as risky. If your cat had some, call your vet.
This information is general and does not replace advice from a veterinarian. If your cat has swallowed something toxic, call your vet or an animal poison control center right away, without waiting for symptoms.