Can dogs eat onions?
Toxic. No. Onions and every other allium damage red blood cells and can cause hemolytic anemia several days after the meal.
Work out the dose for your dog
The amount matters as much as the food. The onion and garlic toxicity calculator for dogs takes your dog's weight and what it ate and returns the dose in mg/kg, with the severity band it falls into.
Open the onion and garlic toxicity calculator for dogs →If it has already been eaten
Your own vet, or the nearest 24-hour emergency animal hospital.
ASPCA Animal Poison Control Center: (888) 426-4435
Pet Poison Helpline: (855) 764-7661
Have ready: your dog's weight, the exact product and how much was eaten, and the time it happened.
How much is dangerous?
Merck reports clinical signs in dogs after 15 to 30 g of raw onion per kg of body weight, and notes that concentrated forms — dehydrated flakes, powders, dried soup mixes — are the usual cause, and that garlic is 3 to 5 times more toxic than onion by weight. Cooking does not reduce the toxicity.
Why it does harm
Sulfur-containing oxidants, released when allium tissue is chopped, cooked or chewed and by gut microbes, oxidize hemoglobin. The damaged hemoglobin clumps into Heinz bodies and the red cells are destroyed, producing hemolytic anemia.
Sources
What to look for
- Vomiting and diarrhea in the first hours
- Weakness, pale or yellow gums, and collapse days later
- Rapid breathing and rapid heart rate
- Red or brown urine
Timing. Digestive upset can be immediate, but the anemia typically appears several days after eating.
What to do
- Call your vet with the type of allium and the amount, remembering that powder is far more concentrated than fresh.
- Mention any packaged food involved: bouillon cubes, baby food, gravy and sauces are the usual hidden sources.
- A normal-looking dog on day one does not mean it is fine. The blood picture is what matters, and it develops later.
Common questions
Can dogs eat cooked onions?
No. Merck is explicit that cooking does not reduce the toxicity. Fried, roasted, raw and dehydrated onion all carry the same compounds, and dehydrated forms concentrate them.
Is onion powder worse than fresh onion?
Yes. Dehydrated flakes, powders and dried soup mixes are the usual cause of poisoning because they pack far more onion into a small amount of food.
Can dogs eat food cooked with onion, like gravy or broth?
It is best avoided. Gravy, bouillon cubes, baby food and sauces are the common hidden sources of onion and onion powder. Check the label on anything savory before sharing it.
How long after eating onion does a dog get sick?
Vomiting and diarrhea can come within hours, but the anemia usually shows several days later as weakness, pale gums and discolored urine. A normal-looking dog on day one is not in the clear.