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My dog ate an onion. Are onions toxic to dogs? What should I do?

Updated On September 23rd, 2025

Pet's info: Dog | Bull Terrier | Male | unneutered | 1 year and 4 months old

Hello , uno just had some pieces of an onion , and he drink almost a full bowl of water 30-45 min after it . Would he be fine ? I heard onions are very toxic for dogs and cats! Thanks In advance for the response

3 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on December 25th, 2016

Onions are toxic to dogs, and it can take a couple of days for toxic signs to appear. It would be best to take Uno into a vet immediately to induce vomiting to get the onions out of his system if he ate them less than two hours ago. Otherwise, you will have to monitor him for signs of toxicity, which include vomiting, diarrhea, blood in urine, lethargy, weakness, yellow gums, and abdominal pain. Should you see any of those signs, I would rush Uno into a vet right away.

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Other Answers

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    Answered By Vanessa Yeager DVM MPH

    Veterinarian

    Published on September 28th, 2017

    Hi and thanks for your post on Petco Pet Education Center, formerly Petcoach this afternoon. Onions as well as garlic can be toxic to dogs causing hemolytic anemia. Onset of symptoms may not be apparent for a few days. Symptoms include pale gums, drooling, vomiting, diarrhea, and weakness. A slice or two of onion may not be enough to cause toxicity, but please keep a close eye on Bongo for the next few days and take him into his veterinarian if he develops any concerning signs as indicated above. Best wishes to you and thank you again for posting!

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    Answered By Andrea M. Brodie, DVM

    Veterinarian

    Published on November 13th, 2018

    Best would be to take her to a petER to have them induce vomiting preferably within an hour of ingestion. Unfortunately the toxic effects of onion and garlic will not show up until about a week later. Signs would be pale gums, excessive tiredness, exercise intolerance, rapid hearty beat, anemia. Once the onion has been regurgitated, however, it is unlikely that your dog will have any ill effects.

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