Why?
Butter is over 80 percent fat and contains very little lactose, so it's less of a problem than milk. Still, that much fat easily causes diarrhea, adds weight and, in large amounts, may contribute to pancreatitis. Salted butter adds sodium on top of that.
How much?
No more than a pea-sized dab, rarely, and only unsalted butter. Never garlic or herb butter, and no buttery dishes.
The risks
- Diarrhea, sometimes vomiting
- Weight gain
- Possible pancreatitis after a large amount
- Salted butter: extra sodium
- Garlic butter or butter with chives is toxic
Your cat ate some: what now?
If your cat licked a little butter off your knife, don't worry. If they ate a good chunk of the stick, watch for vomiting, diarrhea, lethargy or a painful belly over the next 24 to 48 hours, and call your vet if those appear. Garlic butter is worth a call either way.
Better options
A cat treat or a small piece of plain cooked chicken is a much better reward. For hairballs, there are malt-based gels made for cats.
Common questions
Is butter good for hairballs?
It's an old home remedy, but there's no good evidence it works, and it can cause diarrhea. Regular brushing and hairball gels made for cats are better options, and frequent hairballs are worth mentioning to your vet.
Can cats eat margarine?
It's no better: just as fatty, often salted, and full of vegetable oils and additives. Same rule as butter: a lick won't hurt, but don't offer 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.