Can Cats Eat Onions?
Why it’s a problem
Onions contain N-propyl disulfide, a thiosulfate compound that oxidizes and destroys feline red blood cells, causing hemolytic anemia. Cats are several times more sensitive than dogs, and onion powder is the most concentrated form, hiding in soups, gravies, sauces and baby food.
How to serve it safely
Keep all allium dishes away from cats, check labels on leftovers and broths, and clean up dropped food — cats groom what they walk through.
Warning signs to watch for
Lethargy, weakness, pale or bluish gums, drooling, vomiting, rapid breathing and red or brown urine; anemia can worsen for days after ingestion.
When to call the vet
Call your vet the moment you know onions were eaten, even if the cat looks completely normal — treatment before symptoms is far more effective.
Common questions
Is a tiny piece of cooked onion in stew dangerous?
Yes, it can be. Cooking does not destroy the toxin and broth concentrates it. Cats are so sensitive that even small doses matter.
How quickly do symptoms appear?
Stomach upset can start within hours, but the anemia typically shows up 2 to 5 days later — which is why early vet contact matters.
More foods for cats
This page is general educational information, not a substitute for professional veterinary advice. Every pet is different — if your animal ate something concerning, contact your veterinarian or a pet poison hotline right away.