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My dog ate a small amount of onion. Is it toxic? Will he be okay?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 16 lbs

My 16 lb. dog ate a few small slices of onion (I think) from a McDonald’s hamburger. Knowing onions are toxic but given the small amount will he be ok?

2 Answers

Most Helpful Answer

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Answered By Linda G, MS, DVM

Veterinarian

Published on October 12th, 2018

Hello. You have nothing to worry about with this small amount of cooked onion. The problems associated with ingesting onions usually occur with chronic, long term ingestion possibly from a bored dog eating onion grass outdoors or home cooking for a pet & an owner not realizing that onions may cause problems . An occasional bite will never cause a problem. All will be fine. Thanks for using Petco Pet Education Center, formerly Petcoach.

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27Pet Parents found this answer helpful

Other Answers

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    Answered By C. Rathjens, DVM

    Veterinarian

    Published on November 19th, 2017

    Onions are definitely toxic to dogs, but they do have to eat a decent amount to have problems. I have never seen a dog have problems from a single onion slice. If it was a large amount of onion (say 1/4 an onion if he's under 20lbs or 1/2 an onion if he's more), it would be worthwhile to call the ASPCA poison control line to confirm that it was below the toxic dose. If Riley ate the hamburger and bun along with the onion, he may have diarrhea or vomiting from the high protein/fat meal. If the intestinal upset continues more than 24 hours, I would recommend seeking veterinary help (but this would be unrelated to the onions). Good luck and thanks for using Pet Coach!

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    13Pet Parents found this answer helpful

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