Answer-first
Can cats drink milk?
No — despite the cliché, most adult cats are lactose intolerant. After weaning they stop making enough lactase, so cow's milk commonly causes diarrhea (often within 8–12 hours), bloating, and stomach upset. It's also fatty and offers nothing your cat needs. Fresh water is the drink; milk is a myth.Fact
Kittens drink their mother's milk (or kitten formula), not cow's milk. Adult cats need water, not dairy.
Applies to: Adult cats. Nursing kittens are a separate case (queen's milk or kitten milk replacer — see weaning page).
Steps
Why it upsets themFact
- Lactase (the enzyme that digests milk sugar) drops after weaning — most adult cats can't digest lactose
- Undigested lactose draws water into the gut → diarrhea, often within 8–12 hours, plus bloating/upset
- Cow's milk is also high in fat and adds unneeded calories
What about 'cat milk' / lactose-free?Professional guidance
- Specialty lactose-reduced 'cat milk' is safer than cow's milk but is a treat, not a need — count the calories
- Plain water is what your cat actually needs; wet food adds most of its hydration
- No milk fixes hydration better than fresh water and wet food do
If your cat already had milkProfessional guidance
- A one-off small amount usually means temporary loose stool at worst
- Persistent diarrhea/vomiting, or any in a kitten, is a vet matter
- Don't make milk a habit 'because he likes it'
Normal vs keep-watching
Normal: A cat that drinks water and gets hydration from food, with no dairy in the diet.
Keep watching: Any diarrhea/upset after dairy exposure (a reason to stop offering it).
When to contact a vet. Ongoing diarrhea or vomiting, or any digestive upset in a kitten, is a veterinary matter — this page never diagnoses; dehydration from diarrhea is a real risk in small cats.
What changes this answer
- Kitten (needs queen's milk / KMR, never cow's milk)
- Lactose-free 'cat milk' (treat only, count calories)
- Already lactose-reactive (avoid all dairy)
Common mistakes
- A saucer of milk 'as a treat'
- Assuming cats need milk
- Cow's milk for orphan kittens (use KMR — see weaning)
- Ignoring the calorie/fat load
Sources
- ASPCA (animal-welfare authority; PRIMARY tier 1-2) · Tier 2 · verified 2026-07-22
Real questions cat owners ask
- Is milk bad for cats?
- Can cats have lactose-free milk?
- Why do cats like milk if it's bad for them?
No dairy to log — but do track water intake in This Week if hydration is your concern. Set up your Cat Passport.