Can cats eat onion? No — why, and what to do
Quick answer: No — onion is not safe for cats and should never be given.
Quick verdict
Unsafe
Key risk
Cats are especially sensitive; even small amounts can cause anaemia.
Why
Onion is highly toxic to cats and must be avoided.
Can cats eat onion, and why?
Onion is highly toxic to cats and must be avoided. Cats are especially sensitive; even small amounts can cause anaemia.
Cats are obligate carnivores: they must get most of their nutrition from meat and need nutrients such as taurine that only animal products provide. They lack some enzymes for processing plants and carbohydrates, so fruit and veg offer little benefit and can upset their stomach; many cats are also lactose intolerant.
Warning — what to watch for
Cats are especially sensitive; even small amounts can cause anaemia.
If your cat has eaten onion, don’t wait for symptoms — contact your vet immediately, or call the Animal PoisonLine on 01202 509000 (24/7, UK). Signs of a problem can include vomiting, diarrhoea, drooling, lethargy, tremors or loss of appetite.
🚨 Find an emergency vet near youMore foods cats might eat
Keep onion out of reach
If your cat has eaten onion, ring your vet — do not wait to see what happens. For preventing a repeat:
Plush Snuffle Foraging Mat
A roll-up plush snuffle mat with cute animal designs. Hide treats in the folds and let your pet sniff and forage to find them - a rewarding enrichment game that beats boredom and slows feeding.
£13.99
Tarhong Paw Ikat Teal Pet Placemat – BPA-Free PVC & EVA
A vibrant teal ikat placemat with paw print accents — BPA-free, wipe-clean, and 29 × 48 cm for protecting floors under pet bowls.
£8.49
Tarhong Concentric Circle Slow Feeder Bowl for Dogs & Cats
A stylish slow-feeder bowl that encourages healthier, calmer mealtimes — available in blue, grey, or white.
£14.99
Tarhong Country Orchard Melamine Pet Saucer
A pretty fruit and floral orchard-print melamine saucer for pets — BPA-free, non-slip, shatterproof, and dishwasher safe at 13.2 cm.
£9.49
Feeding & nutrition guides
Frequently asked questions
Can cats eat onion?
Unsafe. Onion is highly toxic to cats and must be avoided.
What happens if my cat eats onion?
Cats are especially sensitive; even small amounts can cause anaemia. If your cat has eaten onion, contact your vet or the Animal PoisonLine (01202 509000) straight away — don’t wait for symptoms.
Is onion poisonous to cats?
Unsafe. Onion is highly toxic to cats and must be avoided.
Free printable: safe & toxic foods for cats
onion is just one food — get the full one-page checklist of what’s safe, fine in moderation, or dangerous for cats. Vet-sourced, yours to print and keep.
Check onion for another pet
Sources
Our verdict on whether cats can eat onion draws on established UK and US veterinary and welfare organisations. Individual pets, quantities and preparation vary — always confirm with your own vet.