Leeks, along with garlic, onions, and chives, are members of the Allium family. And while they're all popular and delicious ingredients in kitchens around the country, all allium species are also toxic to cats and dogs.

Eating leek can initially cause symptoms of gastrointestinal upset like vomiting and diarrhea, but it can also damage your cat's red blood cells and cause anemia. The symptoms of toxicity can be slow to develop, and severe cases of leek poisoning have the potential to be life-threatening. With this in mind, it's important to seek urgent veterinary attention if you suspect your cat has consumed any leek.

Keep reading for a guide to the symptoms, causes, diagnosis, treatment, and recovery of leek poisoning in cats.

Symptoms of leek poisoning can appear within 12 hours of your pet ingesting leek, but it may take several days before your cat shows any signs of toxicosis. Symptoms to look for include:

Leeks contain a toxin known as N-propyl disulfide; this substance is what can make your cat so sick. It causes oxidative damage to your cat’s red blood cells, leading to a reduction in their red blood cell count. This means your cat's blood cells are increasingly unable to transport oxygen from the lungs throughout their body, leading to the development of hemolytic anemia.

Take note that your cat doesn't need to consume a large amount of leek for it to be dangerous, as ingesting just 5 grams of onion per kilogram of body weight can cause significant changes to their blood. It's also important to be aware that leek doesn't just pose a risk in raw or cooked form, but that your pet may also come across it in dehydrated flakes or powders.

Be aware that many cases of toxicity occur when small amounts are eaten regularly, building up in the system.

Finally, remember too that other members of the Allium family are also dangerous to your cat. Garlic poisoning is a risk worth being aware of, with the MSD Veterinary Manual explaining that garlic is 3-5 times more toxic than onions. You can find out more about protecting your pet against Allium poisoning in our guides to onion toxicity and chives poisoning.

If your cat has eaten leek, tell your veterinarian how much they consumed, in what form, and how long it's been since ingestion. This information will help them make an accurate diagnosis and decide on the best course of treatment.

Your vet will give your cat a full physical, which will include both a urinalysis and blood work, to assess the extent of poisoning. 

Leek poisoning treatment focuses on supporting your cat and managing their symptoms. The vet may induce vomiting if your cat has ingested leek recently, and administer activated charcoal to absorb the toxins from their system.

In severe cases, your cat may need a blood transfusion to combat anemia, while supplemental oxygen therapy will help carry oxygen to all parts of the body. IV fluids may also be administered to keep your pet hydrated.

As long as you get your cat veterinary treatment soon after eating leek, they have a good chance of making a full recovery. Beginning treatment before red blood cells begin to break down will help your cat to avoid developing anemia. 

However, because of the potential lag time between ingesting leeks and the appearance of the first symptoms, the risk of anemia is high. So even if you only suspect there's a chance that your cat may have eaten a leek, seek veterinary care to get on top of the problem before it develops into something serious.

If severe anemia does develop, your pet will require hospitalization and ongoing monitoring to nurse them back to full health.

Once your cat returns home, make sure to keep them well away from leeks and other toxic foods. Your vet may also recommend switching your cat to a diet lower in potential oxidants to aid their recovery.

Leek poisoning can be expensive to treat. If you suspect your cat is at risk of leek poisoning, start searching for pet insurance today. Wag!’s pet insurance comparison tool lets you compare plans from leading companies like PetPlan and Embrace. Find the “pawfect” plan for your pet in just a few clicks!