Last reviewed: 2026-09-05 · Reference ranges: ASPCA, Pet Poison Helpline & Merck Veterinary Manual
Store your whey protein powder in a sealed, high cabinet your cat cannot access, just like any human medication. Plain whey itself isn't toxic, but the real danger lies in common sweeteners like xylitol, which is extremely poisonous to pets and is found in many powders. Always check the ingredient label for xylitol and never leave an open container or a shaker bottle with residue where your cat can lick it. If you suspect any ingestion, watch for vomiting or wobbliness and contact your vet.
Feed with care · Cats · full breakdown on the linked food page
Plain whey protein is not toxic, but most powders are sweetened — check for xylitol.
The full verdict, portion guidance and serving notes are collected on the Whey food facts page.