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Leeks
Leeks
Leeks (Allium ampeloprasum) are a member of the Allium family — the same group that includes garlic, onions, and chives — all of which are toxic to cats. Leeks contain N-propyl disulfide and related organosulfur compounds that oxidise feline haemoglobin, causing Heinz body haemolytic anaemia. All forms are dangerous: raw, cooked, and dried leeks.
Important Notes
Toxic compounds: N-propyl disulfide and organosulfur compounds (alk(en)yl cysteine sulfoxides); all parts toxic including the bulb, stems, and leaves
Mechanism: oxidative damage to haemoglobin creates Heinz bodies; the spleen destroys affected red blood cells faster than they can be replaced, causing haemolytic anaemia
Symptoms: lethargy, weakness, pale or yellowish gums, rapid breathing, loss of appetite, reddish-brown urine; onset often delayed 3–5 days after ingestion
Leeks in soups, stews, or stir-fries remain toxic after cooking
Never share leek-containing foods with cats; contact your vet immediately if ingestion is suspected
Potentially Toxic Parts
Powder
Juice
Entire Plant
Possible Symptoms Reported in Cats
Tachypnea and Dyspnea (Breathing Difficulties)
Respiratory · After a lag of several days.
Lethargy, Weakness, and Depression
Neurological · After a lag of several days.
Pale Mucous Membranes and Jaundice (Icterus)
Gastrointestinal · After a lag of several days.
Tachycardia (Rapid Heart Rate)
Cardiac · After a lag of several days.
Hemoglobinuria (Dark Urine)
Gastrointestinal · After a lag of several days.
Cold Sensitivity
Neurological · Several days after ingestion.
Because leeks belong to the Allium genus, their toxicosis presents with the exact same clinical signs as onions, garlic
Metabolic
Vomiting, Diarrhea, Abdominal Pain, and Loss of Appetite
Gastrointestinal · Usually within 1 day (24 hours) of ingestion.
Allium Breath Odor
Gastrointestinal · Shortly after ingestion.
Disclaimer: This summary was compiled from multiple sources and is for informational use only. It is not a diagnosis or treatment plan. Toxicity can vary based on the substance, amount, plant part, and individual cat. If you think your cat may have been exposed to a toxic substance, contact a veterinarian right away.