Dog Health
Can Dogs Eat Onion UK?
By Kaiser Khan, EditorPublished Last updated 2 min read
Quick answer
No — dogs must not eat onion. Onions destroy red blood cells, causing anaemia that may appear days later. All forms count — raw, cooked, powder, and in gravy or curry. If your dog ate onion, use our onion toxicity calculator and phone your vet or Animal PoisonLine on 01202 509000.
Key takeaways
- No. Onions contain compounds that destroy red blood cells in dogs, causing haemolytic anaemia. All forms are toxic — raw, cooked, powdered, and in gravy or takeaway food.
- As little as 15–30 g per kg of body weight can cause harm. A few tablespoons of onion gravy or leftover curry may be enough for a small dog. Use our onion toxicity calculator for guidance.
- Vomiting, diarrhoea, weakness, pale gums, rapid breathing, and dark urine may appear within one to five days as anaemia develops.
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Why onion is toxic
Plants in the Allium family — onion, garlic, leeks, chives, and shallots — contain thiosulphates that damage red blood cells, causing haemolytic anaemia.
Hidden sources in UK homes:
- Onion gravy and stock cubes
- Curry, pizza, and takeaway meals
- Baby food with onion powder
- Seasoning mixes
Symptoms
Signs may not appear immediately — anaemia can develop over one to five days:
- Vomiting and diarrhoea
- Weakness and lethargy
- Pale gums
- Rapid breathing
- Dark or reddish urine
What to do if your dog ate onion
- Estimate the amount and note the form (raw, cooked, powder)
- Use the onion toxicity calculator
- Phone your vet or Animal PoisonLine (01202 509000, charges apply) with your dog's weight
- Do not wait for symptoms
See onion and garlic poisoning for full guidance.
Safe alternatives
Plain cooked vegetables without seasoning — carrots, green beans, or plain rice — are safer treats. See what vegetables can dogs eat.
Sources & further reading
This guide draws on the publicly available UK advice listed below. Follow the links for the relevant guidance or the organisation's broader care resources.
PETHEALTH+ is independent. These organisations do not sponsor, approve, or partner with this website. Editorial sources and further reading (last updated 2026-07-19).
Continue exploring
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Also see symptoms, symptom checker, and poison guide.
Frequently Asked Questions
- Can dogs eat onion?
- No. Onions contain compounds that destroy red blood cells in dogs, causing haemolytic anaemia. All forms are toxic — raw, cooked, powdered, and in gravy or takeaway food.
- How much onion is toxic to dogs?
- As little as 15–30 g per kg of body weight can cause harm. A few tablespoons of onion gravy or leftover curry may be enough for a small dog. Use our onion toxicity calculator for guidance.
- What are symptoms of onion poisoning?
- Vomiting, diarrhoea, weakness, pale gums, rapid breathing, and dark urine may appear within one to five days as anaemia develops.
- What should I do if my dog ate onion?
- Phone your vet or Animal PoisonLine on 01202 509000 with the amount and your dog's weight. Do not wait for symptoms — anaemia may take days to appear.