Can my cat drink milk?

Probably not. Most adult cats are lactose-intolerant, and cow’s milk causes diarrhea or other digestive upset, per the ASPCA. The image of a saucer of milk is more cartoon than reality. There’s also a hydration myth here: milk is mostly water, but the upset stomach that follows wipes out any hydration benefit. If your cat seems thirsty and you want to give her something with flavor, a small splash of low-sodium chicken broth or the liquid from a can of tuna in water works much better, and Cornell suggests both as ways to make a bowl more appealing.

When to call a vet: if your cat ate dairy and has diarrhea that doesn’t pass in a day, or seems lethargic, call your vet.