Can Cats Eat Onions?

Updated 18 October 2026 · Researched against PDSA, Cats Protection and International Cat Care guidance

Allium family plants — onion, garlic, shallot, leek, chive — damage red blood cells. Cooking does not make them safe, and onion or garlic powder is more concentrated than the fresh version.

Onion is not only raw or fried: it turns up in stock cubes, gravy granules, soups, baby food, sausages, ready meals and vegetarian 'meat' products. A cat that licks the gravy off a plate can take in a meaningful amount, especially if it happens repeatedly over days.

Signs are often delayed by a day or more because the damage builds as red cells are destroyed, so a cat that seems fine on the evening is not out of the woods. Repeated small exposure from leftovers is the common, easily missed version.

What to watch for in the UK

• Stock cubes and gravy granules are concentrated onion — the Sunday roast plate is the classic route.
• Onion powder in takeaways and ready meals counts as much as the fresh vegetable.
• Sausages, burgers and stuffing often contain onion.
• Never give 'leftovers' as a meal; the seasoning is the risk.

If your cat has already eaten it

1. Phone your vet for advice — the amount, the cat's size and whether it was raw or concentrated all matter.
2. Watch for pale gums, weakness and dark urine over the next few days.
3. Bring the packaging of any stock, gravy or ready meal eaten.

Out of hours, use your practice's emergency number. If you can, take the packaging with you — the ingredient list often tells the vet more than the description does. This page explains risk; it cannot diagnose your cat, and it deliberately contains no doses or home treatments.

If your cat is already vomiting, see the cat vomiting guide and vomiting blood. For the wider red-flag checklist, use sick cat symptoms. If a plant rather than a food is involved, the toxic plants checklist is the right page.

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