If your cat has eaten something toxic, contact your veterinarian, an emergency animal hospital or an animal poison control service right away, even if your cat seems fine. Do not try to make your cat vomit at home.
Why
Onions belong to the Allium family, along with garlic, leeks, chives and shallots. They contain sulfur compounds that damage red blood cells. The damaged cells form clumps called Heinz bodies and then break apart, which leads to anemia. Chopping, cooking and chewing release these compounds, so cooking does not make onion safe.
The Merck Veterinary Manual describes cats as the most susceptible species, followed by dogs. It notes that poisoning has been reported in cats after less than a teaspoon of cooked onion, while dogs usually need to eat much more for their weight before they show signs. Garlic is roughly three to five times more toxic than onion, and dried forms such as onion powder, flakes and soup mixes are especially concentrated.
Signs to watch for
- Signs are often delayed. Damage to red blood cells starts within a day, but anemia usually becomes obvious a few days after the cat ate the onion
- Vomiting or diarrhea soon after eating, from irritation of the stomach and gut
- Lethargy, weakness or hiding
- Loss of appetite
- Pale or yellowish gums
- Fast breathing or a fast heart rate
- Red or brown urine
- Collapse in severe cases
What to do if your cat eats it
- Find out what was eaten and roughly how much: raw or cooked onion, a dish containing onion, or a powder or seasoning. Keep the packaging or recipe.
- Call your veterinarian or an animal poison control service right away, even if your cat seems fine. The worst effects can take days to show.
- Do not try to make your cat vomit at home.
- Your vet may want to repeat blood tests over the following days to check for anemia, even if your cat looks well at the first visit.
- Keep an eye on your cat's appetite, energy and gum color for the next week, and report any change.
Where cats actually find onion
Few cats chew a raw onion. Exposure usually comes from people food that smells of meat or fish and happens to be seasoned. Merck notes that poisoning in cats and dogs is most often linked to concentrated forms such as dehydrated flakes, powders and dry soup mixes. Common sources include:
- Gravy, stock, broth and bouillon cubes
- Leftover meat dishes such as meatballs, burgers, sausages and stir-fries
- Soups, especially those made from dry onion soup mix
- Baby food and other purees seasoned with onion or garlic powder. Check the label before using one to tempt a sick cat to eat
- Seasoning blends, spice rubs and garlic bread
- Chives or green onions growing in a garden or on a windowsill
Is a little garlic good for cats?
No. Garlic is sometimes promoted as a natural flea repellent or health supplement for pets, but it belongs to the same plant family and veterinary toxicology references rate it as more toxic than onion, not less. No amount has been shown to be safe for cats.
The same applies to leeks, chives, shallots and scallions. If a food lists any of them, or onion or garlic powder, among its ingredients, it is not a suitable treat for a cat.
How vets treat onion poisoning
If the cat is seen soon after eating onion, the vet may make it vomit to remove what it can. After that, treatment supports the cat while its body replaces the damaged red blood cells, and the outlook depends a great deal on how much was eaten and how early care starts.
- Repeated blood tests to track the red blood cell count
- IV fluids to help protect the kidneys
- Oxygen, and a blood transfusion if the anemia is severe
Common questions
Are onions good for cats?
No. Onions belong to the Allium family, along with garlic, leeks, chives and shallots.
Are onions bad for cats?
Yes. Signs of poisoning to watch for: vomiting or diarrhea soon after eating, from irritation of the stomach and gut; lethargy, weakness or hiding; loss of appetite.
Are cats allowed to have onions?
No, keep them away from your cat. If your cat eats some anyway: find out what was eaten and roughly how much: raw or cooked onion, a dish containing onion, or a powder or seasoning. Keep the packaging or recipe.
My cat licked gravy that had onion in it. Is that an emergency?
Call your vet or a poison control service and describe the gravy and how much was eaten. A lick of dilute gravy is much less concerning than a plate of onion-heavy leftovers or anything made with onion powder, but they can judge the risk for your cat. If they advise watching at home, look for weakness, a poor appetite and pale gums over the next several days.
Are cooked onions safer than raw onions for cats?
No. Cooking does not destroy the compounds that damage red blood cells. The Merck Veterinary Manual reports poisoning in cats after less than a teaspoon of cooked onion.
Sources
- Merck Veterinary Manual. Garlic and Onion (Allium spp) Toxicosis in Animals.
- ASPCA Animal Poison Control Center. People Foods to Avoid Feeding Your Pets.
- Cornell Feline Health Center. Feeding Your Cat.