Can cats eat onions?

Updated 12/05/2023

While many a dish for us humans begins with softening onions or even a sofrito (if we’re being fancy), can cats eat onions? Afterall, sharing a meal with a loved one is the ultimate bonding experience. Find out here if your furry family members can tuck into the same oniony treats as you…

Are onions poisonous to cats?

The million dollar question: can cats eat onion? Well unfortunately you won’t be sharing your favorite caramelized onion tart with your furry friend any time soon, as it’s a big no for this one. Whether it’s regular small nibbles of something containing ever so slight amounts of onion powder or taking a chunk from the vegetable itself, onion is terribly bad for our feline friends. If you’re still wondering if onions are safe for cats, it’s not an ‘avoid if you can’ type situation here - onions are poisonous to cats, and can cause life-threatening problems.

Why are onions bad for cats?

For cats, eating onions can lead to anemia. How? Well onion toxicity is caused by an oxidant contained in onions (n-propyl disulfide) and unfortunately, the body naturally assumes that this oxidant is a foreign invader. The oxidant attaches itself to the red blood cells, and in an attempt to rid the body of the ‘invader’, it destroys its own red blood cells. This results in the breakdown of red blood cells (otherwise known as hemolysis). With fewer red blood cells being pumped around the body, this can lead to hemolytic anemia, which can be tested for and diagnosed by your vet.

Symptoms of onion toxicity in cats

Hemolytic anemia has a few nasty symptoms that pet parents need to keep an eye out for. If your kitty is suffering, it’s likely they’ll show signs of weakness and panting - caused by the lack of oxygen being pumped around their body. Here are the key symptoms of onion toxicity to watch out for… 

• Weakness
• Lethargy
• Collapse
• Increased heart rate
• Exercise intolerance
• Panting
• Blood in urine (hematuria)
• Vomiting
• Diarrhea
• Reduced appetite
• Shortness of breath
• Pale gums
  

Can cats eat green onions?

No! Green onions are part of the allium family which are poisonous to cats. Green onions have the same effects as other onions and alliums in that they can cause onion toxicity, whether they’re ingested in small amounts over a long period of time or eaten in a large quantity in one sitting.

Can cats eat cooked onions?

Again, it’s a big no! Cooked onions are just as likely to cause onion toxicity in cats, so no sharing your human food, no matter how nice a meal time together can be. Instead, why not simply eat at the same time (or have a snuggle on the sofa with no alliums in sight?).

What to do if your cat eats onions

If your cat has eaten onion or you can see signs of onion toxicity, contact your vet immediately. The effects can be life-threatening, so it’s important to get your kitty checked out as soon as possible. They may do a blood test and blood smear to check your kitty’s red blood cells. Treatment may include supportive treatment, hospitalisation and intravenous fluids. In severe cases of blood loss, a blood transfusion may be needed. 

Meet our veterinary expert, Aisling

This article has been checked by veterinarian Aisling O’Keeffe MVB CertSAM ISFMCertAdvFB. Aisling qualified as a vet 7 years ago from University College Dublin. She has worked in a mixture of UK small animal hospitals along with Irish practices. She worked for 3 years in a feline-only hospital where she further developed her feline medicine and surgery skills. She currently lives and works in a small animal hospital in Cork, Ireland. 

Other foods that aren’t safe for cats

Find out more about what cats can and can’t eat in our handy post to make sure you’re not accidentally feeding your kitty something that’ll cause harm. Here are a few more items your feline friend will need to steer clear of...

• Garlic
• Chocolate
• Cherries
• Tomatoes
• Cheese