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My dog ate a tiny piece of onion. Is it toxic? What should I do?

Updated On September 23rd, 2025

Pet's info: Dog | Dachshund miniature | Male | unneutered | 3 years and 1 month old | 12 lbs

My dog ate the tiniest piece of minced onion, will he be okay? Size of piece shown in photo.

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4 Answers

Most Helpful Answer

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Answered By Dr. Heidi DVM, CVA, CCRT, CVTP, CVSMT, CVCH

Veterinarian, Certified Veterinary Acupuncturist, Certified Canine Rehabilitation Practitioner

Published on October 20th, 2017

The dose of onion in dogs that is toxic is about 0.5 grams per kilogram of body weight. For a 10 pound dog, that would be about 20 grams of onion. There are about 5 grams in each teaspoon, so Marlin would have to eat over 4 tsp of onions in order to be concerned about toxicity. The biggest concern comes with dehydrated onions which are much more concentrated than fresh onions. It sounds like Marlin will be fine, but please contact your veterinarian if you have any concerns. I hope that was helpful! Thanks for using Petco Pet Education Center, formerly Petcoach.

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    Answered By Daniela Jessen, DVM

    Veterinarian

    Published on January 2nd, 2019

    Hi, It all depends on how much she ate and how much she weighs, in general, toxic dose is typically 15-30 grams per kilogram of the dog’s weight (both not specified in the question unfortunately). For now I would suggest to monitor her closely for signs of toxicity such as: lethargy, vomiting, diarrhea, weakness, pale gum and collapse. Bear in mind signs may take several days to manifest so monitor for the next week or so. If it has been less than 2 hours it is worth going to the vet to try induce vomiting.

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    Answered By Daniel Fonza, DVM

    Veterinarian

    Published on November 23rd, 2017

    Hi there and thank you for using Pet Coach! It only takes approximately 100 grams of onion (the size of a medium onion) per 20 kilograms of body weight to cause toxic side effects. This means that a 45-pound dog wound only have to eat a single medium to large size onion to experience dangerous toxic levels. So it depends on how much onion was in the stuffing. If you think it wasn't even close to this amount, Jager will likely be ok. If he ate enough to cause serious side effects and it has been less than 2 hours since he ingested the onion, you can induce vomiting by giving an oral dose or hydrogen peroxide. The dose for this is about 1ml per pound of body weight. Longer than two hours post ingestion and it will have already moved along from the stomach to the intestines and the hydrogen peroxide will not work. You can also call the ASPCA poison control hotline and they can advise you further. I hope this helps! Please let me know if you have any other questions or concerns.

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    Answered By Catherine Stecyk

    Veterinarian

    Published on June 19th, 2019

    Hello and thank you for reaching out to Petco Pet Education Center, formerly Petcoach. Hazel would have to eat a large amount of onion to become sick, so definitely more than little pieces that would be on a burger. The toxic dose is approximately 30 g per kilogram, so if she weighs 2kg, she would have had to eat at least 60g of onion to become sick. I recommend watching for any signs of pale gums, difficulty breathing, or GI signs such as vomiting or diarrhea. If you don't notice any signs in the next couple hours, Hazel will likely be just fine. I hope this is helpful!

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