Can Cats Drink Milk? Why Most Adult Cats Should Not

Most adult cats should not drink milk, because the majority are lactose intolerant and cow’s milk gives them an upset stomach. The classic picture of a contented cat lapping a saucer of milk is a myth: after weaning, most cats lose the ability to digest milk sugar, so that saucer is far more likely to cause diarrhoea than happiness. Cats are obligate carnivores, and a complete cat food plus fresh water already gives them everything they need.

Can cats drink milk?

For most adult cats the honest answer is no. Cow’s milk is not toxic to cats the way onions or lilies are, so a stolen lick will not poison your cat. The problem is digestion: the majority of adult cats cannot break down lactose, the natural sugar in milk, which means even a small bowl can leave them with a sore, gurgling tummy. Milk also brings calories with no benefit your cat’s normal diet does not already cover, so there is no nutritional reason to offer it at all.

Why are most cats lactose intolerant?

Most cats lose the enzyme they need to digest milk soon after they stop nursing. Kittens produce plenty of lactase, the gut enzyme that splits lactose into sugars they can absorb, because their entire early diet is their mother’s milk. Once weaning is complete, usually by around 8 weeks of age, lactase production drops sharply and most cats never make much again. In an adult cat, the lactose in cow’s milk therefore passes undigested into the large intestine, where gut bacteria ferment it and it pulls water into the bowel. Cornell Feline Health Center notes this is why dairy commonly upsets adult cats even though kittens handle milk easily.

What happens if a cat drinks milk?

The usual result is digestive upset within several hours. Signs of lactose intolerance in cats include diarrhoea, vomiting, bloating, gas, and abdominal discomfort, and they typically appear about 8 to 12 hours after the milk goes down. The amount matters: a single lick may do nothing, while a full saucer is much more likely to cause trouble. One bout of mild diarrhoea will usually settle on its own, but if it is severe, bloody, or lasts more than a day or two, or if your cat seems unwell in any other way, that is a reason to call your vet. You can read more about when loose stools need attention in our guide to diarrhoea in cats.

What should cats drink instead?

Fresh, clean water is the only drink a cat actually needs. Water has no calories, supports kidney and urinary health, and should always be available; this matters even more because cats evolved from desert animals and often have a low thirst drive. Many cats drink too little, which is one reason wet food, which is roughly 70 to 80 percent water, is so useful for boosting overall moisture intake. If your cat seems reluctant to drink, the fix is rarely milk: it is usually a cleaner, larger, or better-placed water source. Our guide on how to get a cat to drink more water covers the tricks that actually work, from wide bowls to pet water fountains.

When I first adopted my tabby, Pip, I did the textbook wrong thing and gave her a little saucer of cow’s milk as a welcome treat. She loved it, and then spent the next day with the kind of diarrhoea that taught me my lesson faster than any leaflet could. These days the only thing in her bowl is water, refreshed twice a day in a wide ceramic dish away from her food, and her stomach has never complained since.

Is “cat milk” safe?

Specialist cat milk is safer than cow’s milk, but it is still a treat, not a drink. The cat milk sold in pet shops is made from cow’s milk that has been treated to remove most or all of the lactose, so it is far gentler on a cat’s stomach. That does not make it a health food: it is still calorie-dense, and since treats of any kind should make up no more than about 10 percent of a cat’s daily calories, a little goes a long way. Use it as an occasional indulgence if you like, but never as a replacement for water or as part of the daily diet. For the bigger picture on balancing treats with a complete diet, see our cat nutrition guide, and remember that some human foods are genuinely dangerous: our list of foods toxic to cats is worth keeping handy.

What about cheese, cream, and other dairy?

Other dairy carries the same lactose problem, plus extra fat and salt. Cheese, cream, butter, and ice cream all contain lactose, so they can trigger the same digestive upset, and they are also high in fat and (for cheese especially) salt, neither of which a cat needs. A crumb of cheese now and then is unlikely to harm a healthy cat, but it is not a kind regular habit. If you want to give a treat, a few pieces of your cat’s normal kibble or a small amount of a purpose-made cat treat is a far safer choice than anything from the dairy aisle.

This guide is general information, not a diagnosis. If your cat has ongoing tummy trouble, has drunk a large amount of milk, or you are unsure what is safe to feed, speak to your own vet, who can examine your cat and knows its history.