No. Onions contain sulfur compounds that damage a dog's red blood cells and can cause anemia, according to the Merck Veterinary Manual. Raw, cooked, fried, dried and powdered onion are all a problem, and so are the rest of the onion family: garlic, chives, leeks, shallots and green onions.
If your dog just ate onion, call your vet or a pet poison line today. The damage to red blood cells can take several days to show, so a dog who looks fine tonight is not in the clear yet.
Key takeaways
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- Onion is toxic to dogs in every form: raw, cooked, fried, dried and powdered.
- Garlic, chives, leeks, shallots and green onions do the same harm; garlic is reported as stronger.
- It damages red blood cells, and anemia often shows three to five days later.
- Powder, soup mix and several days of onion-seasoned leftovers carry the most risk.
- If your dog ate onion, call your vet today, even if your dog seems fine.
My dog ate onion: what to do now
- Take away whatever is left and keep your dog from getting more.
- Work out what and how much. Raw or cooked onion, onion rings, a dish with onion powder, dry soup mix? Roughly how much, and when? Keep the package or recipe.
- Weigh your dog, or use their last known weight. The risk depends on how much they ate for their size.
- Call your vet, an emergency vet, or a pet poison line. The ASPCA's advice for the onion family is to call its poison control line or your local vet as soon as possible.
- Keep watching for the next week, even if the vet says to wait and see. Signs of anemia are often delayed.
Go to an emergency vet now if your dog is weak, collapses, has pale or yellow gums, is breathing fast, or has red or dark brown urine.
How much onion is toxic to a dog?
There is no single safe amount, and the published numbers do not agree.
Tap or hover a row to highlight it.
| Source | What it says | For a 22 lb (10 kg) dog | For a 70 lb (32 kg) dog |
|---|---|---|---|
| SourceMerck Veterinary Manual | What it saysSigns reported after 15 to 30 grams of raw onion per kilogram of body weight | For a 22 lb (10 kg) dog150 to 300 g of raw onion | For a 70 lb (32 kg) dogabout 480 to 950 g of raw onion |
| SourcePetMD | What it saysProblems consistently noted above 0.5% of body weight in onion (5 g per kg) | For a 22 lb (10 kg) dog50 g of raw onion | For a 70 lb (32 kg) dogabout 160 g of raw onion |
Being under either number does not make it safe. These figures are for fresh raw onion only, and several things push the risk up:
- Powder and dried onion are concentrated because the water is gone. There is no reliable way to convert a spoon of onion powder into grams of fresh onion, so any amount of powder or dry soup mix is worth a call.
- Garlic is generally reported as 3 to 5 times more toxic than onion (Merck).
- Small amounts over several days add up. A dog fed leftovers with onion every day can get sick from amounts that would not matter once.
- Some breeds are more sensitive. Pet Poison Helpline names Japanese breeds such as the Akita and Shiba Inu.
- Small dogs get a much bigger dose from the same bite.
Signs of onion poisoning, and when they show up
Vomiting, diarrhea, drooling, a sore belly or not wanting to eat can come early, within the first day.
The red blood cell damage usually shows later. Pet Poison Helpline says the main signs are often seen three to five days after a dog eats onion powder. In a study where dogs were given garlic for a week, their blood counts were lowest on days 9 to 11, according to Lee and others, 2000. Watch for:
- weakness or tiring quickly on walks
- pale, grey or yellow gums
- fast breathing or a racing heart
- red, orange or dark brown urine
- collapse
A vet can check a blood sample for the changes onion causes before a dog looks sick. Severe cases can need oxygen or a blood transfusion, according to Merck.
Foods that hide onion
Most onion poisonings are not a dog eating a raw onion. They come from people food:
- gravy, stuffing and stews, especially at Thanksgiving and Christmas
- pizza, burgers and meatloaf
- soups, broth, bouillon and dry onion soup mix
- onion rings and fried onions
- baby food, some brands of which contain onion powder
- seasoning blends, garlic salt and onion salt
- Chinese, Mexican and Indian takeout, which often use onion, garlic and green onion
If a dog ate a food with onion in it, bring the label or list the ingredients when you call. Fatty foods like gravy and pizza can also cause stomach upset or pancreatitis on their own.
"My dog has eaten onion before and was fine"
That happens, and it can be true. Whether a dog gets sick depends on how much they ate for their weight, what form it was in, whether it happened once or several days in a row, and the dog. A little onion in a big dog's dinner once may do nothing visible. The same amount in a small dog, or as powder, or every day for a week, can cause anemia. And because the signs are delayed, a dog who seemed fine that evening may not have been fine a few days later. Keep onion out of your dog's food, and call when it gets in.
Check what you learned
Quick check
Questions about dogs and onions
What happens if a dog eats a little bit of onion?
A small piece of cooked onion in a large dog may cause no visible problem, or a mild upset stomach. It is still worth a call to your vet, especially for a small dog, powder, or a dog who has had onion several days running, because the anemia shows up days later.
Is cooked onion safe for dogs?
No. Cooking does not make onion safe, and cases have involved cooked and butter-fried onion.
Can dogs eat food cooked with onion, like broth?
Better not. Broth, stock and bouillon often contain onion or onion powder. Use plain broth with no onion or garlic, or plain water.
Are green onions and chives toxic to dogs?
Yes. They are in the same family as onion. The ASPCA lists onion, garlic and chives among foods that can damage red blood cells.
Is onion toxic to cats?
Yes, and cats are more sensitive to it than dogs.
Sources
Checked September 24, 2026.
- Merck Veterinary Manual, Garlic and Onion (Allium spp) Toxicosis in Animals (reviewed September 2024)
- Pet Poison Helpline, Onions and Onion Powder Poisons Probing Pooch
- ASPCA, People Foods to Avoid Feeding Your Pets and Garlic
- PetMD, Can Dogs Eat Onions?
- Lee KW and others, Hematologic changes after garlic extract in dogs, American Journal of Veterinary Research, 2000