Why?
Meat sauce is almost always made with onion and garlic, which damage a cat's red blood cells even when cooked. The layers of ricotta, mozzarella or béchamel are high in fat and lactose, which often lead to vomiting and diarrhea. Add salt and herbs, and it's a dish that doesn't belong in a cat's bowl.
How much?
No amount is recommended. Don't leave a pan of lasagna cooling on the counter unattended.
The risks
- Anemia from onion and garlic
- Diarrhea from the lactose in cheese and sauce
- Vomiting, or pancreatitis from the fat
- Far too much salt for a small body
Your cat ate some: what now?
Call your vet without waiting for symptoms, especially if your cat ate the sauce: onion-related anemia can take several days to appear. Tell them how much was eaten and what was in it, and don't try to make your cat vomit.
Better options
A little ground beef cooked separately, with no salt or onion, will make your cat much happier. Just set some aside before you season the sauce.
Common questions
Can cats eat the meat from lasagna?
No, because it has simmered in the sauce with onion and garlic, and rinsing won't remove them. If you want to share, set aside some plain cooked ground meat before seasoning it.
What about lasagna noodles?
Plain cooked pasta isn't toxic, but noodles taken from a lasagna are coated in sauce and cheese. Your cat gains nothing from them, so skip it.
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.