Onions and garlic destroy red blood cells in dogs and cats — raw, cooked, powdered or dried, it makes no difference. The scary part is the delay: a pet can seem fine for days while anemia develops. Powder and soup mixes are the concentrated traps. Check the dose below, then read what to watch for.
🧅 Onion & Garlic Toxicity Calculator
Assumes ~110 g per medium onion and ~5 g per garlic clove. Onion/garlic powder is roughly 3–4× stronger than fresh — if powder or soup mix was eaten, treat one level more seriously and call your vet.
Why are onions and garlic toxic?
All allium plants — onion, garlic, leek, chives, shallots — contain compounds that oxidise hemoglobin in pets’ red blood cells, forming “Heinz bodies” that make the cells rupture. The result is hemolytic anemia: too few red cells to carry oxygen. Cats are roughly twice as sensitive as dogs, and Japanese breeds (Akita, Shiba) are more vulnerable than average.
How much is dangerous?
Reported toxicity starts around 5 g of onion per kg of body weight for dogs (about half an onion for a 10 kg dog) and roughly half that for cats. Garlic is more potent gram-for-gram — treat a few cloves in a small dog seriously. Repeated small amounts over days are as dangerous as one big amount: the damage accumulates.
Symptoms to watch (1–5 days)
Weakness and tiring on walks, pale or yellowish gums, fast breathing or heart rate, dark reddish-brown urine, vomiting, reduced appetite. Any of these after known allium exposure = vet immediately, mention exactly what was eaten and when.
Hidden sources
Onion soup mix and stock cubes, gravy, baby food (often onion-powdered), pizza and takeaway leftovers, sausage and seasoned meats, fried onion toppings, garlic bread — and “natural flea remedy” garlic supplements, which are a myth with real risks.
FAQ
My dog ate a little cooked onion in food — panic?
Run the numbers above. A small dose in a large dog is usually below the toxic range — but powders concentrate fast, and repeat exposure accumulates. When near the line, call.
Is a little garlic good for dogs?
No — the “garlic for fleas” claim has no supporting evidence and documented toxicity. Skip it.
How is allium poisoning treated?
Early: induced vomiting and activated charcoal at the clinic. Later: supportive care, IV fluids, and in severe anemia, blood transfusion. Most pets recover well when treated before severe anemia sets in.
This tool is a triage aid, not a substitute for veterinary care. When in doubt, call your vet — find an emergency vet here.
