The full answer
Leeks are an Allium species. The Merck Veterinary Manual names leeks alongside onion, garlic and chives, and describes Allium toxicosis in dogs as oxidative damage to red blood cells that can lead to haemolytic anaemia.
VCA Animal Hospitals states that all forms are poisonous to dogs, including raw, cooked, dried, powdered and liquid preparations. Cooking a leek doesn't remove the risk.
Leeks are a common base for soups, stocks, gratins, pies and dried soup mixes. These foods need the same caution as the vegetable itself, and dried mixes are more concentrated.
Both the white stem and the green leaves are part of the same plant.
Risks and Things to Know
- Allium compounds can damage red blood cells and cause haemolytic anaemia.
- Cooking does not make leeks safe.
- Leek soup, stock and dried soup mixes carry the same hazard.
- Signs can be delayed by several days.
How much is okay?
No amount of leek is suitable for a dog.
Keep trimmings, leftovers and leek-based dishes out of reach.
How Should I Prepare It?
- Leeks have no safe preparation for dogs.
- Do not pour leftover soup or cooking stock over your dog's food if it was made with leek, onion or garlic.
