What are the symptoms of Onion poisoning in cats?

pale or white gums, lethargy and weakness, rapid breathing or panting, vomiting and diarrhea, reduced appetite, reddish-brown urine (hemoglobinuria), elevated heart rate

Onion

Q: Can cats eat Onion?

Dangerous: Never — extremely toxic to cats. Far more dangerous than for dogs. Onions are significantly more dangerous to cats than to dogs. Cats lack sufficient levels of the enzyme glucose-6-phosphate dehydrogenase (G6PD), making their red blood cells highly vulnerable to oxidative damage from thiosulfates and organosulfur compounds found in onions. This causes Heinz body anemia — a condition where red blood cells are destroyed faster than they can be replaced. Cats are affected by much smaller doses relative to body weight than dogs. Even a small amount of onion in any form — raw, cooked, dehydrated, powdered, or in juice — can trigger a life-threatening crisis. Source: ASPCA.

Dangerous

Verdict

Never — extremely toxic to cats. Far more dangerous than for dogs.

Toxic principle: thiosulfate, organosulfur compounds (Heinz body anemia — cats far more susceptible)

Source: ASPCA · Verified 2026-06-12

If your cat ate this

Cats hide symptoms — don't wait and see. Even small amounts of certain substances can be fatal to a cat. Act fast.

1. Call your veterinarian immediately
US — National hotline: ASPCA Animal Poison Control Center (888) 426-4435 aspca.org(24/7, Consultation fee may apply.)
US — National hotline: Pet Poison Helpline (855) 764-7661 petpoisonhelpline.com(24/7, $89 per incident fee; also covers Canada.)
GB — National hotline: Animal PoisonLine 01202 509 000 animalpoisonline.co.uk(24/7, £35 per call (8am–8pm weekdays), £45 at other times.)
AU — National hotline: Animal Poisons Helpline 1300 869 738 animalpoisons.com.au(24/7)
NZ — National hotline: Animal Poisons Helpline 0800 869 738 poisons.co.nz(11am–7pm NZ time (currently being extended), Charges apply.)
CA — National hotline: Pet Poison Helpline (855) 764-7661 petpoisonhelpline.com(24/7, $89 per incident fee.)

Verified 2026-08-06

Verdict

Onions are significantly more dangerous to cats than to dogs. Cats lack sufficient levels of the enzyme glucose-6-phosphate dehydrogenase (G6PD), making their red blood cells highly vulnerable to oxidative damage from thiosulfates and organosulfur compounds found in onions. This causes Heinz body anemia — a condition where red blood cells are destroyed faster than they can be replaced. Cats are affected by much smaller doses relative to body weight than dogs. Even a small amount of onion in any form — raw, cooked, dehydrated, powdered, or in juice — can trigger a life-threatening crisis.

Symptoms to watch for

• pale or white gums
• lethargy and weakness
• rapid breathing or panting
• vomiting and diarrhea
• reduced appetite
• reddish-brown urine (hemoglobinuria)
• elevated heart rate

What to do

This is a veterinary emergency. Contact your vet or ASPCA Poison Control (888-426-4435) immediately. Blood tests will be needed to check red blood cell count. Treatment may include IV fluids, blood transfusions in severe cases, and monitoring for delayed anemia that can develop days after exposure. Remove all onion-containing foods from your cat's reach.

ASPCA Animal Poison Control Center: (888) 426-4435 aspca.org