Why?
Leeks contain the same kinds of sulfur compounds as onion and garlic. These oxidize red blood cells, which weaken and are destroyed, causing Heinz body hemolytic anemia. Every part of the plant is involved, and cooking doesn't reduce the toxicity enough to make it safe.
How much?
No amount is safe. Watch for hidden sources: vegetable soups, potato leek soup, quiches, tarts and broths, where leek is often blended in and invisible.
The risks
- Hemolytic anemia (destruction of red blood cells)
- Pale gums, weakness, fatigue
- Dark or reddish urine
- Vomiting, diarrhea, loss of appetite
- Symptoms that can appear several days later
Your cat ate some: what now?
Call your vet or an animal poison control center right away, without waiting for symptoms: anemia can take several days to show. Don't make your cat vomit yourself. Note what it ate, how much and when.
Better options
If you're making soup, set aside a piece of cooked zucchini or carrot for your cat before adding the leeks.
Common questions
My cat ate potato leek soup, what should I do?
Call your vet right away, even if your cat shows no symptoms. They'll tell you whether it needs treatment now or monitoring with a blood test, since anemia can appear days later.
Are leek greens toxic to cats?
Yes. Both the white and green parts contain the toxic compounds. Keep trimmings out of reach, including in the trash or compost.
This information is general and does not replace advice from a veterinarian. If your cat has swallowed something toxic, call your vet or an animal poison control center right away, without waiting for symptoms.