How much onion is dangerous?
Many vets treat about 0.5% of body weight in onion (5 g/kg) as a concerning dose; the Merck Veterinary Manual reports clinical signs at 15-30 g/kg. The table shows the amount of fresh onion reaching the 0.5% body-weight level. Powdered onion is far more concentrated.
| Dog weight | Fresh onion at threshold | Roughly |
|---|
| 10 lb | 22.7 g | ≈ 20.6% of a medium onion |
| 20 lb | 45.4 g | ≈ 41.2% of a medium onion |
| 40 lb | 90.7 g | ≈ 82.5% of a medium onion |
| 60 lb | 136.1 g | ≈ 123.7% of a medium onion |
| 80 lb | 181.4 g | ≈ 164.9% of a medium onion |
Smaller amounts are not "safe": effects build up over several days of exposure, and individual sensitivity varies.
Symptoms to watch for
- Vomiting, drooling and diarrhea
- Weakness and lethargy
- Pale gums
- Fast breathing, rapid heart rate, red or brown urine (often 1–5 days later)
Why it is dangerous
Risks
- Damage red blood cells (Heinz body anemia)
- Onion powder is concentrated and hides in soups, gravy, baby food and seasoning
- Effects can build up when small amounts are eaten over several days
How to keep your dog safe
- Never feed onions, leeks, chives or shallots
- Check gravy, broth and leftovers for onion
- Call your vet after any significant ingestion
What to do if your dog ate onions
- Work out how much was eaten, when, and your dog's weight. Keep any packaging.
- Call your vet or animal poison control now: ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661.
- Do not make your dog vomit unless a vet tells you to.
- Follow your vet's advice even if your dog seems fine: treatment works best before signs start.
Related: How much onion is toxic to dogs?
Safer treats to give instead
These are safe for dogs in treat-size amounts:
Planning treats? Check your dog's full daily needs with the dog food calculator or dog calorie calculator.
Onions and dogs: FAQ
Can dogs have onions?
No. Onions are toxic to dogs in all forms: raw, cooked, dried and powdered. They damage red blood cells and can cause anemia. Signs are often delayed by several days.
How much onion is toxic to dogs?
The Merck Veterinary Manual reports clinical signs in dogs after 15–30 g/kg of raw onion. Many vets use a more conservative threshold of about 0.5% of body weight (5 g/kg), and repeated small amounts add up.
Is cooked onion safe for dogs?
No. Cooking does not destroy the toxic compounds.
What about onion powder?
It is more concentrated than fresh onion, so small amounts in seasoned foods can matter for small dogs.
Can puppies eat onions?
No. Puppies are smaller and more vulnerable than adults, so the risks are greater. Call your vet if your puppy ate any.
More "can dogs eat" guides
Browse lists: all vegetables dogs can eat · human foods dogs can eat · foods dogs can't eat
Sources
This guide is general information for healthy adult dogs. Dogs with medical conditions (such as diabetes, pancreatitis, kidney disease or food allergies) may need different advice from their vet.