How Long Does It Take For Onions To Kill A Dog

How Long Does It Take For Onions To Kill A Dog?

Last Updated: August 18, 2023
correct answerThe Short Answer is:

It may take up to 72 hours for the toxin to start wreaking havoc in your dog’s blood. There is plenty of time to get to the vet and prevent major organ and tissue damage caused by a lack of oxygen.

In this article you will know the answer to the query “How Long Does It Take For Onions To Kill A Dog?“.

Its okay if you’re worried that your dog just stole a hamburger from the dinner table.

How Long Does It Take For Onions To Kill A Dog

No matter how much onion is in the hamburger it would not kill your pet.

However it is crucial that you understand the dangers that onions pose to dogs.

Burger may give your dog an upset stomach but if your pet eats a medium-sized onion he might be in trouble particularly if you have a Chihuahua or another small breed of dog. 

We’ll explore why onions are dangerous to dogs how to recognize onion poisoning and what to do if your dog becomes poisoned by onions. 

Why are onions toxic for dogs?

One of the biggest problems you will face if you eat an onion is bad breath. Dogs can be dangerous if they eat an onion. 

Onion contains a chemical compound called N-propyl disulfide which can not be processed by dogs.

As the compound attaches itself to oxygen molecules in the red blood cells it can cause extensive damage.

Therefore if the red blood cells fail in their primary function of transporting oxygen to tissues and organs the dogs immune system will begin to view them as invaders.

When bacteria or viruses are present in an organism the immune system attacks them and thats usually a good thing.

Nevertheless if the immune system begins to destroy red blood cells in a process called hemolysis your dog will develop hemolytic anemia which is potentially fatal.

What parts of the onion are dangerous to a dog?

It is toxic to dogs in all parts of the onion including the flesh leaves and juice. It does not matter whether the onion is cooked or raw the toxic compound is still there.

A second danger many people overlook is onion powder which is found in many foods you may buy at the supermarket.

In onion powder the N-propyl disulfide concentration is higher than in raw onion. You should always read the labels carefully before serving any type of processed food to your pet be it canned food soup or sauce. 

Which are the main symptoms of onion toxicity?

Whenever your dog eats food containing onions you need to watch out for any symptoms of onion poisoning.

If you do not know how much onion the dog ate you will need to monitor him carefully if you are unsure how much he ate. You do not want to wait until he becomes sick to take action. 

Here are the most common symptoms of onion poisoning:

  • Lethargy
  • Weakness
  • Reduced appetite
  • Pale gums
  • Fainting
  • Reddish urine
  • Vomiting
  • An elevated heart rate
  • Excessive panting

As soon as you notice any worrying signs take him to the vet if he has been raiding the pantry or eating something containing onions.

Alternatively if you catch your dog eating onions in your vegetable garden do not wait at all.

He is more likely to avoid serious consequences if he gets medical attention as soon as possible. 

How long does it take for the symptoms to appear?

In order for the toxic compound in onion to be fully absorbed into the body it may take up to 24 hours. It may take up to 72 hours for the toxin to start wreaking havoc in your dogs blood. There is plenty of time to get to the vet and prevent major organ and tissue damage caused by a lack of oxygen. 

It is important to keep in mind that the negative effects of onion build up over time. During the course of several days if the dog ingests a moderate amount of onions he might develop the same level of toxicity as that produced by eating a few full onions at a time. 

How much onion can kill a dog?

A dog can consume up to 0.5% of its body weight in onions without showing any signs of poisoning experts say. Up to 2.5 ounces of onion will not cause serious health problems for a 30-pound dog but anything above that will put his life at risk. Consider that the average weight of a small onion measuring 1-2 inches in diameter is 2.46 oz. It should be noted that this is the average weight and some onions can weigh as much as 5.3 oz which is way above the safety limit. 

What can I do if my dog ate onions?

If you suspect your pet ate a couple of onions or indeed any amount over the safety limit you should contact your veterinarian as soon as possible. In the event that you can not reach your veterinarian you might be able to induce vomiting yourself. There is a possibility that the onion might still be in the dogs stomach if he just ate.

If he had stolen some food containing onions hours ago it would have already been digested and had reached the dogs intestines by now so there is no need to make him vomit. It takes an average of two hours for food to pass through a dogs stomach.

Activated charcoal can also be given to your dog to counteract the toxic effects caused by onions. There are many forms of activated charcoal available for dogs including liquid capsules tablets and powder. Having charcoal in your medicine cabinet is always a good idea if you have a dog since it can be used as an emergency treatment for various types of toxins. 

Nevertheless these are emergency measures you can take but you should have your pet checked out by a professional as soon as possible. 

How is onion poisoning treated?

In addition to examining your pet your veterinarian will likely order some blood tests to see if the toxic compound is already affecting the red blood cells. If the tests indicate that your dog has hemolytic anemia he will probably require a blood transfusion.

In this case your dog may have to spend the night in the hospital for observation. As soon as he is discharged it is recommended that he rest as much as possible. Exciting activities and long walks are not recommended.

He should also be put back to sleep after going outside and doing his business. A few days later the vet might need to perform another blood test to see if the dogs red blood cells count is back within normal range. 

You can expect a full recovery for your dog if you seek immediate medical attention. As soon as N-propyl disulfide is out of his system his bone marrow will start producing new blood cells and he’ll be back to normal in a few days.

Are some dogs more susceptible to onion poisoning?

In addition to dogs cats are also toxic to onions. On the other hand studies indicate that certain breeds of Japanese descent are more likely to develop serious side effects from eating onions. The Japanese chin is one of these breeds as well as Akitas and Shibas.

What other vegetables are toxic to dogs?

Onions garlic chives and leeks which are all members of the Allium family are toxic to dogs. Dogs should avoid garlic as much as possible. Researchers have found that dogs’ red blood cells can be damaged by 15-30 grams of garlic per kilogram of body weight.

Garlic cloves weigh between 3-7 grams so a dog would have to eat quite a bit of it to be in any real danger. Garlic powder on the other hand needs to be handled carefully. Garlic powder is commonly used to season dishes and it is also found in many processed foods but one teaspoon of garlic powder contains the same amount of toxins as several cloves.

What are some dog-friendly vegetables?

Vegetables are important components of a dogs diet as they provide vitamins and minerals. You can feed your dog various types of fruit such as apples bananas and berries as well as carrots and sweet potatoes as they are both great sources of vitamins. 

If you make sure they do not contain onions or garlic theres no reason not to give your dog some meatballs or hamburgers. If you substitute shredded carrots and cheese for onion and garlic you can make some delicious meatballs for your dog. Its best not to give your dog a lot of cheese as too much salt is also bad for them.


Dogs should never be fed onions because they are toxic to them. The best thing you can do if your dog manages to eat a few bites of some onion-containing food is to have him checked by a vet as soon as possible but if he eats a lot you might want to take him to a vet as soon as possible.

Even if the dog seems fine at the moment onion toxicity can develop between 24 and 72 hours after exposure. Onion poisoning rarely causes death but if treated properly the prognosis is very good. 

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Amanda Dogs Trainer

Amanda (Author)

With over a decade of experience, Amanda is a distinguished dog trainer. Her expertise in canine behavior has transformed countless lives, fostering harmonious human-canine connections. Through compassionate and personalized approaches, she empowers owners to understand and connect with their furry companions, creating a legacy of joyful tails and transformed lives.

Osvaldo Maciel Dogs Trainer

Osvaldo Maciel (Content Reviewer)

Osvaldo Maciel, a stalwart in the field with 14 years of experience, is a revered dog trainer. His journey is defined by a profound understanding of canine behavior, shaping unbreakable human-canine bonds. Osvaldo guides owners to connect with their beloved pets, leaving an indelible mark of happiness and transformation. His legacy shines through the countless lives he has touched.

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