Onions: Safe or Poisonous for Felines?

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Onions are a delicious addition to many dishes, but can cats eat onions? While onions can be beneficial for humans and even some other animals, the answer is unfortunately no. You may think that giving your cat a bit of onion every now and then won’t hurt them, however this could not be further from the truth.

Let’s take a look at why onions are not suitable for cats and what you should avoid feeding your pet.

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Toxicity in Onions

Onions contain sulfur-based compounds called thiosulfates which can cause anemia in cats if ingested in large enough quantities. These compounds damage the red blood cells by causing oxidative stress which leads to decreased oxygen supply throughout the body.

More specifically, compounds in onions transform hemoglobin in the blood to emthemoglobin which in turn causes hemolytic anemia and the formation of Heinz bodies on the edges of red bloods cells (source).

The severity of the symptoms depends on how much onion was consumed, as well as the size of your cat. 

Which Parts are Toxic?

All parts of the onion plant—including the leaves and stems—are toxic to cats due to their thiosulfates content. Garlic is also toxic because it belongs to the same family as onions; however garlic is more potent than onions so it should be avoided even more strictly than its milder counterpart.

Be sure to keep all parts of these plants out of your cat’s reach!

Other Foods That Contain Onions

It’s important to note that many human foods contain onions or garlic as ingredients; this includes:

  • canned soups
  • sauces
  • dips
  • dressings
  • gravies
  • condiments like ketchup or BBQ sauce

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If you feed your cat wet food or treats from a can or pouch then check the label carefully before giving them any!

You should also avoid feeding them any table scraps that contain onions or garlic such as pizza toppings or casseroles.

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Symptoms to Watch Out For

If you suspect that your cat has ingested some onions or garlic then it is important to watch them closely for any signs of toxicity. The most common symptoms include:

  • vomiting
  • diarrhea
  • decreased appetite

More severe cases may include:

  • pale gums
  • lethargy
  • difficulty breathing
  • overall lack of coordination

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What to Do if Your Cat Ate Onions

If you notice any of the symptoms above or suspect that your cat has eaten onions or garlic then it is important to seek veterinary care as soon as possible.

Your vet will likely want to perform a blood test to check for anemia and may recommend a course of treatment if necessary.

The best way to prevent onion toxicosis in cats is to keep them away from all parts of the onion plant, as well as any human foods that contain onions or garlic. When in doubt, always check the label!

Diagnosis of Onion Toxicity in Cats

Diagnosing onion toxicity in cats typically involves a physical exam to look for signs of anemia such as pale mucous membranes.

The veterinary specialist may also review the medical history of the cat to uncover any recently eaten foods that contain onions or onion-containing products.

To confirm a diagnosis, a blood smear is often taken and examined under a microscope for Heinz bodies on the edge of affected red blood cells.

In severe cases, a complete blood count (CBC) can be performed to check for hemolytic anemia as further evidence of onion toxicity.

Treatment of Onion Toxicity in Cats

Onion toxicity in cats can be a serious health concern but luckily it is treatable with immediate professional medical attention. Unfortunately, there is no single antidote or magic bullet; however, depending on the severity of the case, monitoring, and supportive care to ensure that the cat gets ample rest and sustenance may be all that is needed.

In more intense cases, intravenous fluids and hospitalization could be necessary and in time bone marrow will usually create new healthy red blood cells to replace the damaged ones.

In very rare and severe cases, blood transfusions may even need to be administered to replenish their vital oxygen stores, but this type of measure isn’t typically necessary.

If left untreated, however, onion toxicity in cats can cause a wide range of unpleasant side effects so always reach out for help if symptoms are present!

Cost of Onion Toxicity Treatment in Cats

The cost of onion toxicity treatment in cats will depend on the severity and length of hospitalization as well as any additional tests or blood transfusions that may be necessary.

In general, the cost of treating anemia due to onion toxicity can range from a few hundred dollars up to a couple thousand depending on how quickly the cat responds to treatment and if any additional complications arise.

The best way to save on medical costs is to take precautionary measures and keep your cat away from all parts of the onion plant as well as foods containing onions or garlic!


As you can see, feeding your cat onions will do more harm than good! Even if they seem interested in eating these vegetables it’s best to only give them food specifically formulated for cats with no added spices like garlic or onion powder. If you suspect that your cat has eaten an onion then contact your vet immediately as treatment needs to be administered promptly to minimize any long-term effects on their health. With proper care and nutrition, your kitty will stay happy and healthy for years to come!

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