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What is Onion Poisoning?

The longer you wait to take your cat to a veterinarian, the worse his symptoms may become. To avoid complications, take your cat to a veterinarian as soon as possible after you spot the symptoms of onion poisoning.

Many people use onions to add flavor to their favorite dishes, but unfortunately, onions are toxic to various animals, including cats. In fact, it is believed that cats are more sensitive to the toxins of onions than other animals such as dogs or horses. Even a small amount of the bulb, flower, or stem of an onion can trigger a response in your cat. Once it is consumed, the onion causes oxidative damage to your cat’s red blood cells, which impacts the bloodstream’s ability to transport oxygen to different organs in the body. This condition, known as Heinz body anemia, can be incredibly dangerous.

Symptoms of Onion Poisoning in Cats

Some cats begin to experience symptoms of onion poisoning soon after ingestion, however other cats may not exhibit any symptoms for several days. Some of the most common symptoms to look for include:

  • Excessive drooling
  • Vomiting
  • Diarrhea
  • Pale colored gums
  • Physical collapse
  • Pain in the abdomen
  • Weakness
  • Lethargy
  • Elevated heart rate
  • Elevated respiratory rate
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Causes of Onion Poisoning in Cats

Onion poisoning occurs after a cat consumes onion, which can be poisonous in both fresh and dried forms. Every part of the onion, including the bulb, flowers, and stem, are toxic to cats. 

An onion can cause oxidative damage to red blood cells, known as Heinz body anemia, making it impossible for the cat’s bloodstream to transport oxygen to different parts of the body. 

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Diagnosis of Onion Poisoning in Cats

If you see your cat eating onion or if you notice any of the symptoms above, take him to a veterinarian as soon as possible for treatment. Talk to the vet about the symptoms you have observed, when they began, and if possible, when your cat consumed onion. 

The vet will begin by taking basic tests to look at the cat’s overall health. These tests include a complete blood count, blood chemistry profile, and urinalysis. These tests will show an abnormally low level of red blood cells, and when a blood sample is analyzed closely, the vet should be able to spot Heinz bodies, which indicates the cat is suffering from hemolytic anemia.  

A number of different conditions can cause hemolytic anemia, so the presence of Heinz bodies does not always lead directly to a diagnosis of onion poisoning. The vet will rely heavily on the symptoms you have described when making a diagnosis, so be as clear and informative as possible.

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Treatment of Onion Poisoning in Cats

Treatment will begin immediately following the diagnosis of onion poisoning. The vet will need to induce vomiting to remove any of the onion that remains in your cat’s stomach cavity. To do so, a 3% hydrogen peroxide solution will be administered orally. Following the induced vomiting, the vet may also administer activated charcoal, which will absorb any toxins that still remain in your cat’s stomach cavity. A gastric lavage, which is a type of stomach wash, may also be performed to flush out your cat’s stomach.

If your cat’s skin has also come into contact with an onion, the vet will thoroughly bathe and scrub your cat to remove any toxins lingering on the skin. 

Many cats become dehydrated either before or during treatment because of the vomiting and diarrhea. If this happens to your cat, the vet will need to provide him with fluids via an IV. 

In extreme cases, the cat may have already lost too many red blood cells by the time you take him in for treatment. If this has happened to your cat, a complete blood transfusion may be necessary.

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Recovery of Onion Poisoning in Cats

The sooner you take your cat to a veterinarian for treatment, the better his chances are of making a full recovery. If your cat has already suffered severe red blood cell loss by the time he receives treatment, his chances of recovering are much lower.

The vet may keep your cat following treatment to ensure he has been stabilized and no longer needs IV fluids or respiratory support. Once your cat has been released to you, discuss his diet with your vet. It’s important to remove any foods that may contain onion from your cat’s diet. In the days following treatment, the vet may recommend you stick to softer foods to avoid upsetting the cat’s sensitive stomach. Keep your cat comfortable and calm while he regains his strength over the next several days.

Make sure your cat does not have access to any onions. If you keep these out on your kitchen counter for cooking, put them in a safe place where cats cannot come into contact with them.

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Onion Poisoning Questions and Advice from Veterinary Professionals

Need pet health advice? Ask a vet

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damian

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Bombay

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10 Years

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Mild severity

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Mild severity

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Puking

my cat got into some onion grass two days ago and has since puked it up twice , i gave him some water today and he does eat a bit and became playful after i engaged him, he has not gone potty that much mabe twice since then is he ok or do i need to give him more water i was not that much mabe a blade or two of that grass

Sept. 19, 2018

damian's Owner

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julia, cheeto, tippy, etc

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Not sure

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2 Months

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Fair severity

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Fair severity

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None Yet

i gave my cats food that had 2% or less onion in it and im really scared because i don't have the money for a vet. should they be okay? some of the pets who ate it are 2 months old

July 28, 2018

julia, cheeto, tippy, etc's Owner

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3320 Recommendations

A small quantity of onion shouldn’t cause much of an issue, however it isn’t the specific percentage of the food with onion but the actual quantity (how many grams per kilogram body weight or ounces per pound body weight) consumed; monitor the kittens for any signs of pale gums or gastrointestinal upset. Regards Dr Callum Turner DVM

July 28, 2018

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Ingmanang

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Bombay Cat

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11 Months

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Mild severity

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1 found helpful

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Mild severity

Has Symptoms

Vomit

Hello there Wag! I've been waiting for your response about that onion toxicity because my cat start to vomit again. He vomit after the day he take the 7 slices of onion, last night and this morning he started to vomit again. He threw up what I fed to him. However, I have also notice that here's no sign of pale and weaknesses of him. I'm so worried because I don't have enough money to bring him in Veterenarian. :( Please reply quickly. Please. :----(

July 27, 2018

Ingmanang's Owner

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3320 Recommendations

I replied to your question around 24 hours ago, I’m not sure why it didn’t go through. Onions are toxic for cats and can cause haemolytic anaemia among other things, the vomiting is just due to gastrointestinal upset from initially consuming the onions; it is important to check Ingmanang’s gums, if they are pale he will definitely need treatment by a Veterinarian. Fluids are best, to keep hydration but if you can try to visit a charity clinic or other organisation for an examination. Regards Dr Callum Turner DVM

July 27, 2018

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Leo

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Munchkin/manx

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3 Years

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Fair severity

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2 found helpful

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No Symptoms
No Sympt

I just heard that onions are toxic to cats and my 11pound cat was just caught chewing on the onion stems. He is not showing any signs of being sick but i am worried about him. He only ate a couple of tops but i want to he sure he is ok!

June 29, 2018

Leo's Owner

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3320 Recommendations

Onions are toxic to cats and may cause at a minimum some gastrointestinal symptoms but at the worst haemolytic anaemia; I’m not sure about the toxicity of the stems compared to the onion itself but I would recommend monitoring Leo for the time being and visit your Veterinarian if any symptoms present like pale gums, lethargy or anything else concerning. Regards Dr Callum Turner DVM

June 29, 2018

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Linhs

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Black cat

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5 Years

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Fair severity

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Fair severity

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Nothing Yet

My cat just ate a piece of an onion off my sandwich and I didn’t realize they were bad for her but then I read that they are toxic and I was wondering what a little piece of onion will do to my cat?

Feb. 11, 2018

Linhs' Owner

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3320 Recommendations

Linhs should be alright with the amount consumed, but if you have some activated charcoal I would recommend that you administer that to help absorb any toxins in the gastrointestinal tract; if you notice lethargy, pale gums or anything else concerning visit your Veterinarian. There are various different figures for toxicity but I quote the figure of 5mg/kg (2.5mg/lb) based on the article below: “Cats are considered more sensitive to onion toxicosis than other species are. Exposures > 5 g/kg can result in gastrointestinal upset, oxidative damage of hemoglobin (resulting in hemolysis), Heinz body anemia, methemoglobinemia and secondary renal damage from hemoglobinuria. If anemia develops, it is generally regenerative unless there is a preexisting health condition.” http://veterinarymedicine.dvm360.com/pungent-poisoning-onion-toxicosis-cat

Feb. 11, 2018

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Hector

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DOMESTIC

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8 Months

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Mild severity

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None Yet

In cleaning off the balcony I brought my plants inside and went back out to grab something. By the time I came back my 8 month old cat had chewed on the tips of my potted green onion. There are chew marks all over the shoots and the tip of one is missing, maybe a 1/2 inch at the absolute MOST. It's been about 45 mins, he's acting relatively normal so far. Cleaned his box so I can watch for stool issues and am keeping an eye on him. I know onions are toxic over time but he had such a small amount, should I be overly worried? He hasn't vomited at all yet, he sneezed a few times but I did have the windows open at the time, maybe he has seasonal allergies? He played for the past 30 mins, drank some water and went for a nap, all normal for this time of day. Please let me know if I should be doing something different, inducing vomiting or something. Thanks.

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Mellow

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Persian

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2 Months

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Fair severity

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Hi, I gave my cat a table spoon and a half of some instant chicken ramen noodle soup and I didnt realize there might he onion powder in the seasoning so now I'm worried about him because idk what amount was in there or not. It's only been an hour so there arent signs.

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Persephone

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Grey longhaired tabby

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3 Years

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Mild severity

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Fever
Stumbling
Diarrhea?

My cat has been stumbling around i took her to the vet yesterday he thinks its meningitis. But I JUST thought, that a couple days ago i made sausage with peppers and onions in it. She may have gotten into it. Im not sure though.. I need to know/wanna ask if the symptoms shes showing could be a result of onion poisoning?

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Cora

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long hair

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4 Months

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Fair severity

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No Symptoms

My kitten go ahold of my McDonald’s cheeseburger I know it had onions and pickles on and I’m not sure how much of that she ate she’s only 3 lbs. I know the burger has diced onions but with her size I’m worried it was too much for her. She just had her vet appointment this morning and received her last round of shots including her rabies vaccine. I’m not sure how worried I should be.

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Cosmos

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Domestic shorthair

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1 Year

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Fair severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

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None

My cat Cosmos just ate the cheese off about 40% of a small pizza. He also ate the toppings attached, including pineapple, broccoli, tomato sauce, and onions. It was probably about 1/8 of a small onion. His brother might have also eaten some of it, but I imagine it was just the one cat. So far, he has no symptoms. It was probably 1 to 2 hours ago. Should I take him to the vet or just monitor him?

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