Can Dogs Eat Cooked Onions?

Onion is a culinary delight that adds an extra kick to every meal.

Throw in a handful of cooked onions in your chicken broth and snuggle down on the couch when it’s dull and chilly.

While you may enjoy cooked onions in various ways, you can’t help but wonder if the same applies to your pup.

Well, we’re about to find out.

Can dogs eat cooked onions?

No, dogs can’t eat cooked onions as they contain a toxic substance called thiosulphate that can damage your dog’s red blood cells, causing anemia. 

This article will answer the commonly asked questions about cooked onions and their effects on dogs.

It will also discuss the potential dangers of cooked onions to your dog and why you should avoid them altogether.

Can Dogs Eat Cooked Onions

Are cooked onions toxic to dogs?


Onions in whatever form, cooked, raw, or powdered, are highly toxic to dogs as they contain a chemical compound called thiosulphate.

Thiosulphate can cause potentially fatal Heinz body hemolytic anemia in dogs. 

The condition causes oxidative damage to your dog’s red blood cells by linking to the oxygen molecules in your pup’s red blood cells, shortening their lifespan.

The red blood cells then rupture in a process called hemolysis, causing hemolytic anemia.

Worse still, it can result in death if left untreated.

This red blood cell breakdown may affect your dog’s liver and kidneys.

Onions can also upset the lining of the intestines, which can cause pain and diarrhea.

How much onion can be poisonous to dogs?

Dogs have varying sensitivity, so this toxic amount may depend on an individual and the amount consumed.

Some dogs may eat cooked onions and experience mild GI distress, or none, while others may suffer severe clinical symptoms.

Generally, 5 grams of onion per kilogram body weight may not cause irreparable harm to your pup.

However, if your dog eats more than half a percent of its body weight in onion, he may develop toxicity if left untreated.

While some dogs may be a bit more resistant to more onions than recommended, it’s best to avoid it as any amount of cooked onion is potentially a risk.

The toxicity levels can accumulate if you feed your dog tiny amounts regularly.

What to do if your dog accidentally eats cooked onions

While a tiny bite is not enough to be lethal for your dog, it’ll be worth contacting your vet for advice.

Large quantities of cooked onions may cause lethargy, weakness, reddish urine, or fainting in dogs.

In case your dogs accidentally eats cooked onions, these are the steps you can take:

Avoid further contamination

Keep away the cooked onion leftovers or any onion product to prevent further access.

Clean up any spills and keep your dog out while doing this.

Give plenty of water

Try to keep your dog hydrated with fresh drinking water at frequent intervals while keeping an eye on signs of lethargy, loss of appetite, or weakness.

Find out the details

Try to find out how much cooked onion your dog has eaten and, if possible, the exact time it happened.

Your vet will need this information to administer the correct treatment.

Don’t self medicate

While you may want to control the situation at home or give first aid, it’s best to rush your pup to the vet for proper care.

Treating onion toxicity at home may derail the chances of a better outcome and may be too late when you seek professional help.

Contact your vet

If your dog consumes cooked onions, it’s best to call your vet to explain the situation, as treating the symptoms early might save your dog’s life.

Provide your vet with every detail you’ve gathered, which will help when starting treatment.

You can also contact an emergency clinic if your family vet is unavailable to help provide urgent vet care.

How long after eating cooked onions will a dog get sick?

The side effects of your dog eating cooked onions may start to show within 1 to 3 days.

The symptoms may range from mild to severe.

Usually, it can begin as a stomach upset, including vomiting, diarrhea, cramping, lethargy, and loss of appetite.

Your dog may also suffer anemia and even death in the long run.

Anemia occurs when your dog’s red blood cells get damaged, overwhelming the cells’ antioxidant properties.

This, in turn, changes the shape of the red blood cells, causing rupture.

When red blood cells rupture, less oxygen is transported to your dog’s tissues, organs, and muscles, causing anemia, weakness, organ failure, or death.

Symptoms of onion toxicity

Some dogs may show onion toxicity within a day after consuming cooked onions.

However, to some, it may take several days for symptoms to start to show.

Some of the signs of onion toxicity may include:

  • Loss of appetite
  • Pale gums
  • Weakness
  • Lethargy
  • Fainting
  • Red tinge to the urine
  • Vomiting
  • Diarrhea
  • Elevated heart rate
  • Panting

If your dog experiences any or all of these symptoms, take him to the vet immediately to prevent fatalities.

How are dogs treated for onion toxicity?

Generally, the treatment for onion toxicity will depend on the amount consumed and the exact time your dog ingested it.

Getting your pup to the vet soon after he eats cooked onions can make a world of difference.

The vet may induce vomiting or administer activated charcoal as a preventive measure.

However, if your dog experiences onion toxicity, he may require treatment such as intravenous fluids or a blood transfusion. 

Your dog may also undergo supportive care to keep his body going while flushing out the toxins and replacing the damaged red blood cells.

Can dogs eat onion rings?

You shouldn’t feed your dog onion rings even in small quantities, as they are even worse for your dog.

Along with the toxins that can damage your dog’s red blood cells, onion rings involve deep-fat frying that may cause your dog to vomit or have diarrhea.

Your dog may also experience rapid weight gain, which can increase the chances of obesity, heart disease, and gastrointestinal issues.

Healthier alternatives to feed your dog instead of cooked onions

There are plenty of more nutritious and safer snacks you can offer your dog instead of cooked onions.

For example, you can give your dog:

  • Blueberries
  • Pitted apples
  • Carrots
  • Asparagus
  • Celery
  • Zucchini

As with any treats, you can start by giving your dog tiny bites while monitoring for any reactions.

You can increase the amount gradually without going overboard.

In conclusion

Avoid feeding your dog cooked onions as there are far too many potential risks.

There are plenty of healthier snacks like apples or zucchini that will contribute to your dog’s overall health without worrying about possible symptoms and dangers.

Always consult your vet before offering your dog human foods such as cooked onions to rule out poisoning.

Megan Turner

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