Macadamia nuts — Food safety facts
Do not feed · Cats · full breakdown on the linked food page
Toxic to dogs — weakness, wobbliness and tremors within 12 hours. Usually recoverable, but call your vet.
Dogs and cats carry the same rating (Do not feed), so the notes below hold for either pet.
Macadamia nuts 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.
The full verdict, portion guidance and serving notes are collected on the Macadamia nuts food facts page.