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Onion & garlic toxicity calculator
Your dog or cat ate onion or garlic? Enter their weight and how much they ate to see how it compares with amounts that have caused poisoning.
How the amount compares with poisoning doses, and what to watch for, will show here.
This tool helps you judge urgency; it does not replace a vet. Last reviewed October 7, 2026.
Why onions and garlic are toxic to pets
Onions, garlic, leeks, shallots and chives all belong to the Allium family. They contain compounds that damage red blood cells in dogs and cats, which can lead to anemia. Raw, cooked, dried and powdered forms are all toxic.
How much is dangerous?
These figures come from the Merck Veterinary Manual's chapter on garlic and onion toxicosis:
| Pet | Amount that has caused signs |
|---|---|
| Dog | 15–30 g of raw onion per kg of body weight |
| Cat | 5 g of raw onion per kg, or less than a teaspoon of cooked onion |
| Garlic | 3–5 times more toxic than onion |
The calculator divides the amount eaten by your pet's weight and compares it with the lower end of those figures: 15 g/kg for dogs and 5 g/kg for cats. For garlic it multiplies the amount by 3 to 5 first. Concentrated forms such as onion powder, dried flakes and soup mixes are especially dangerous, so the calculator doesn't estimate a dose for them. Call your vet instead.
For example, a 30 lb (13.6 kg) dog would need to eat about 200 g of raw onion to reach 15 g/kg. The same dose of garlic is only about 40–70 g.
Signs and timing
Damage to red blood cells starts within 24 hours and usually peaks around 3 days. The resulting anemia typically shows 3 to 5 days after eating, so a pet can seem fine at first. Watch for:
- tiredness, weakness or not wanting to exercise
- not eating
- fast breathing or a fast heartbeat
- yellow gums or eyes
- red or brown urine
If your pet ate a large amount, or any amount of onion powder or garlic, call your vet straight away. Treatment works best before red blood cells are damaged. Don't try to make your pet vomit at home unless a vet tells you to.
Questions people ask
How much onion is toxic to a dog?
Signs have been reported in dogs after eating 15 to 30 g of raw onion per kg of body weight. For a 20 lb (9 kg) dog that is about 135 g or more. Garlic is 3 to 5 times more toxic.
Is cooked onion safe for dogs?
No. Cooking doesn't remove the toxic compounds, and dried or powdered onion is even more concentrated. Ready-made foods such as gravy and soup often contain onion powder.
Why are cats more sensitive than dogs?
Cats' red blood cells are more easily damaged by the compounds in onions and garlic. Poisoning has been reported in cats after less than a teaspoon of cooked onion.
How long after eating onion will a dog get sick?
Usually a few days. Red blood cell damage begins within 24 hours, but anemia typically shows 3 to 5 days after eating.
Is a little garlic good for dogs?
Garlic is 3 to 5 times more toxic than onion for dogs and cats. Ask your vet before giving any garlic-based supplement.