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My cat ate onion stems. Is a small amount toxic? Should I worry?

Updated On September 23rd, 2025

Pet's info: Cat | Himalayan | Female | spayed

I just caught my cat eating the onion stems of the onions I was starting indoors. I looked up online to see if it was toxic and they said it is, so now I am worried. I don't think she ate very much of it and so far she is ok. Should I do anything?

4 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on May 7th, 2020

Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Pretty. I understand your concern, and yes onions are toxic to cats. That being said, if she didn't eat very much, it won't affect her. A small amount won't cause any problems. I hope this helps!

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    Answered By Dr. Davis

    Veterinarian

    Published on March 9th, 2018

    No she will be fine. Animals need to eat a lot of onions to get sick and cats are more fussy than dogs so they generally do not eat enough. Just keep and eye on her, she may have a mild stomach upset or diarrhea but both are unlikely. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Clemmy.

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    Answered By Dr. Melanie, BVSc MS

    Veterinarian

    Published on February 16th, 2017

    Oh no! Consumption as little as 5g/kg of onion can cause toxicity in cats. For Purcell, that would mean he would have to 11g of onion to cause toxic symptoms. If it was less than a gram, then he should be ok, but I would refrain from feeding him anything with onions in it in the future. If you are concerned that he did have close to 11g of onion, I would have him seen by a vet immediately for decontamination procedures to prevent onion toxicity from occurring. This would include inducing vomiting with a shot, IV fluids, and any other treatment the vet deems necessary. Hopefully, he will be ok, and it's always best to have a vet check done right away if you are concerned.

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    Answered By Daniela Jessen, DVM

    Veterinarian

    Published on December 30th, 2018

    Cats are more susceptible to onion/garlic toxicity than dogs. Toxicity can occur whether the products are fresh / cooked / in a dried/powdered form. In cats, ingesting 5 g/kg or more of onion is considered a risk for causing anemia. The onset time for developing anemia can be as soon as 12 hours after ingestion, but it is typically delayed up to 2-5 days after the exposure. Initial clinical signs of onion poisoning in cats can be nonspecific, the most common signs are vomiting, diarrhea and lethargy. If you suspect your cat ingested the toxic dose mentioned above and it has been less than 2 hours of ingestion, I recommend taking the cat directly to your vet or an emergency vet so that vomiting can be induced. If you are not sure how much the cat ate monitor closely for the next week by keeping the cat indoor and watching including monitoring urine and stool in the litter box. Any changes in behavior, reduced activity, pale or white gums , vomiting/diarrhea and urine color changes take her immediately to the vet. Good Luck

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