Can Dogs Eat Onions?

Picture of dog on the floor

We love to share so many of our favorite foods with our dogs. We’re always wondering if it’s safe for a dog to eat things. One food that it’s definitely NOT safe for your dog to eat, in any form, is onions. Here’s why.

Are Onions Toxic?

Onions contain a toxin called N-propyl disulfide. This is a compound that can break down red blood cells, resulting in anemia in dogs. (It’s even more toxic for cats to eat onions.)

The toxin causes oxidative damage to your dog’s red blood cells. It attaches to the oxygen molecules in your dog’s red blood cells so they have a reduced ability to carry oxygen. This also makes your dog’s body think that the blood cell is an invader. Your body destroys the red blood cells in a process known as hemolysis. This results in something called hemolytic anemia.

Are All Parts of the Onion Toxic to Dogs?

Every part of the onion plant is toxic to dogs. That includes the flesh and bulb of the onion, its leaves, onion juice, and even processed powders. Whether an onion is raw or cooked, fried, boiled, or in a powder, onions are toxic to dogs. The same goes for the rest of the allium family which includes garlic, shallots, leeks, and chives. They are all harmful to dogs.

It only requires about 100 grams of onion (the size of a medium onion) per 20 kilograms of a dog’s weight (a kilogram is 2.2 pounds) to see toxic effects. That means that a dog that weighs 45 pounds only has to eat one medium to large-sized onion to experience a dangerous level of onion toxicity. Many dogs will happily munch on a bag of onion rings or eat an onion casserole if they have the chance, so this is something dog lovers need to watch.

Onion powder is found in a wide variety of foods including soups and baby foods. Onion and garlic powders are even stronger than fresh onions. If you are thinking of giving some human food to your dog, it’s always a good idea to check the label to see if the food contains onion or garlic powder. These are ingredients that you should try to avoid.

You will occasionally see garlic added as an ingredient in some dog foods or used as an herbal remedy for dogs. In these cases the amounts used have to be very small and, we hope, they are being used by a skilled practitioner or veterinary nutritionist.

Symptoms of Onion Poisoning in Dogs

If you believe your dog has eaten onions, here are some signs of anemia to check for:

  • Decreased appetite
  • Fainting
  • Lethargy
  • Pale gums
  • Panting
  • Reddish urine
  • Weakness

If your dog is showing any of these symptoms, take him to a veterinarian right away. Your vet can diagnose your dog’s condition through his symptoms and bloodwork. The formation of Heinz bodies can be detected with a blood smear.

Dogs can develop other forms of anemia that have similar symptoms so it’s important for your veterinarian to give your dog a thorough exam. Be sure to let your vet know that your dog has eaten onions so s/he will consider their affect.


If your dog develops onion toxicity, your vet may induce vomiting, depending on how recently your dog ate the onions. Your dog may need supportive care until he can begin producing healthy red blood cells to replace the damaged cells. In severe cases, your dog may need a blood transfusion.

Onion toxicity or onion poisoning can be fatal to dogs so the faster you take your dog to the vet for treatment after eating onions, the better the prognosis.


The best way to avoid health problems associated with onion toxicity is to prevent your dog from eating onions in any form. Onion and garlic powders are more potent than fresh onions but onions in any form can be toxic to your dog. If you are thinking of giving your dog any foods for humans, check the labels and make sure they don’t contain onions. It only takes a relatively small amount of onion to affect your dog. Keep onions and all members of the allium family (shallots, chives, leeks, and garlic) away from your dog.



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