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Dog Onion Toxicity Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Purnima Singh, PhD and Adena Benn
Based on research by
Harvey, J. W., & Rackear, D. Experimental onion-induced hemolytic anemia in dogs.; Veterinary Pathology; 1985See 5 more sources
VCA Animal HospitalsOnion, Garlic, Chive, and Leek Toxicity in Dogs;The American Kennel ClubCan Dogs Eat Onions?;Kingsdale Animal HospitalOnion Toxicity In Dogs: How To Spot The Symptoms;American Society for the Prevention of Cruelty to AnimalsToxic and non-toxic plants: Onion;Kovalkovičová et al. Some food toxic for pets; Interdisciplinary Toxicology; 2009
Last updated: Jan 18, 2024

Welcome to the dog onion toxicity calculator, one of our tools aimed at the safety of our beloved pets.

Onions, garlic, and leek can be poisonous for both dogs and cats, and they're all easily accessible and widely used in almost all cuisines worldwide. That's why it is crucial to know the amount that may be harmful and the proper way to react in case of toxicosis.

Follow our article below to find out:

  • How to recognize the symptoms of onion poisoning in dogs;
  • What to do if you know your dog has eaten onions; and
  • Whether dogs are allergic to onions or not;

We'll also talk about the following:

  • Dog garlic toxicity;
  • Dog chive toxicity; and
  • Dog leek toxicity.

🍫 Want to know more about other products that are dangerous for our furry friends? Check out the dog chocolate toxicity calculator or the cat chocolate toxicity calculator.

Are onions bad for dogs?

To sum it up — YES, they are. 🧅

Onions, garlic, leek, and chives all contain a substance called N-propyl disulfide, a toxin characteristic for the allium plants that give them their specific, spicy taste.

N-propyl disulfide can easily break down the red cells in your dog's blood, causing vomiting, severe anemia, or even death. The dogs are not allergic to onions; these plants act just like a simple poison.

How much of an onion is toxic to a dog?

It is estimated that even the equivalent of 0.5% of your dog's weight, given in onions, may cause severe toxemia.

It all means that the toxic dose for a 10 kg (22 lb) dog amounts to 50 grams (1.8 oz), a mass equal to that of 1/3 of a medium onion.

The effects of consuming such an amount may include altered pet behavior and severe anemia. Remember, these signs and symptoms might be life-threatening.

❗ If your dog ate some onions, and you're unsure about the specific amount — don't hesitate to look for professional help.

Contact your vet if you are in doubt.

What happens if a dog eats onions?

When a dog eats onions, the toxin (N-propyl disulfide) enters its body and cannot be broken into smaller particles; the substance further blocks the enzymes in your dog's red blood cells, causing hemolysis, and in turn, their death. The blood cannot carry enough oxygen to the vital organs without sufficient red blood cells.

Since we don't know exactly how much of an onion is toxic to a dog, and your dog in particular, it is always better to be on the safe side!

What are the symptoms of onion poisoning in dogs?

Some symptoms of onion poisoning in dogs include:

  • High heart rate;
  • Decreased appetite;
  • Panting;
  • Fainting;
  • Vomiting;
  • Breakdown of red blood cells (hemolytic anemia, Heinz body anemia);
  • Blood in the urine (red/pink urine); and
  • Yellow eyes.

Onion poisoning may result in death.

What should I do if I know my dog ate onions?

The list is short:

  1. Contact your vet.

The professionals will treat and monitor your dog. The treatment may include intravenous fluids, oxygen support, or blood transfusions.

If you cannot reach a professional veterinarian service, call the pet poison control hotline. In such a case, they may have to guide you through inducing vomiting in your dog at home using a substance such as the 3-percent hydrogen peroxide solution.

How to use the dog onion toxicity calculator?

Just two steps are needed:

  1. Enter the weight of your dog.
    Use a unit of your choice.
  2. Enter the amount of onion consumed by your dog.
    • Small onion weights ~100 g (3.5 oz);
    • Medium onion weights ~150 g (6 oz); and
    • Large onion weights ~230 g (8.1 oz).

Your results will immediately appear underneath the calculator.

💡 Our dog onion toxicity calculator uses the 0.5% of your dog's weight as a threshold for Serious toxicity — the amount that may cause life-threatening effects, according to, this study. We arbitrarily marked the Toxic dose as 0.25% of your dog's weight to increase the method's sensitivity and decrease the number of undetected cases.

🙋 We, the creators of the dog onion toxicity calculator, sincerely hope that you're here only for educational purposes; if so, we may also interest you in the dog size calculator and the dog calorie calculator.


What is the onion toxicity dose for a 10 kg dog?

The toxicity dose for a 10 kg dog can be as low as 25 grams! That's when the first signs & symptoms might start to appear.

However, severe toxicity that might be life-threatening shouldn't be experienced if the consumed dose doesn't exceed 50 grams.

Remember, a dog's susceptibility varies. Since you can never be too sure, it's always a good idea to consult your vet!

How do I calculate the onion toxicity amount for my dog?

There are calculations that just should be quick. Fortunately, dog onion toxicity dose is one of them.

  1. Find out your dog's weight.

  2. Use one or two of the following equations

    Toxic dose (g) = Dog's weight(kg) × 2.5

    Serious toxicity dose (g) = Dog's weight(kg) × 5

  3. That's it!

    You've just calculated the amount of onions that might be toxic for your dog.

Łucja Zaborowska, MD, PhD candidate
Your dog's weight
Consumed amount
Your dog's toxic doses
Toxic dose
Serious toxicity
🧄 Remember that onions contain the same poisonous substance as garlic, chives, and leeks.
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