Rhubarb — Food safety facts
Do not feed · Cats · full breakdown on the linked food page
Leaves contain high levels of oxalates that can cause kidney failure; the stems are also risky in quantity. Keep rhubarb away from pets.
Dogs and cats carry the same rating (Do not feed), so the notes below hold for either pet.
Rhubarb should not be given to cats at all. Even a small amount can do harm, so there is no portion small enough to be safe.
Do not induce vomiting and do not give milk or oil to “dilute” it. Note the food and roughly how much was eaten, then call your vet or a pet poison hotline and follow their advice on whether to bring the pet in straight away.
Why these cautions matter
A heavy salt load drives up thirst and urination, and in the worst cases leads to sodium ion poisoning, which is a genuine emergency.
Rhubarb has no place in everyday feeding: keep the rest of the day's food unchanged after this and watch the litter box and how quickly they finish the next meal.
The full verdict, portion guidance and serving notes are collected on the Rhubarb food facts page.