Why is it safe?
Commercial cat milk products (Whiskas Cat Milk, Catisfaction, GimCat Drink) are specifically formulated with the lactase enzyme added or with lactose pre-digested, reducing lactose content to levels that do not trigger the osmotic diarrhea caused by standard cow's milk in adult cats. They contain no alcohol, no caffeine, no methylxanthines, and no artificial sweeteners. These products are nutritionally supplementary, not a dietary staple.
Symptoms
None at appropriate serving sizes. Excessive amounts may cause soft stools, the products retain trace lactose and have a high fat content relative to water.
What To Do
No action needed. Fresh water must always be available alongside, cat milk does not replace water as the primary hydration source.
Notes
Do not confuse with cow's milk (MEDIUM risk — see separate entry), plant-based milks (oat, almond, soy — not appropriate for cats, no nutritional benefit and contain additives), or homemade lactose-free milk (human lactose-free cow's milk still contains proteins that cause GI upset in some cats and is not equivalent to a formulated cat milk product). Kitten Milk Replacer (KMR — brands include Royal Canin Babycat Milk, Beaphar Kittenmelk) is the correct product for kittens under 4 weeks needing supplemental feeding; it is formulated to match queen's milk composition and is not interchangeable with adult cat milk products.
Sources
→ Cornell Feline Health Center — vet.cornell.edu
→ VCA Animal Hospitals — vcahospitals.com
→ International Cat Care — icatcare.org