Even a few grapes or raisins can cause acute kidney failure in dogs. There is no known safe dose — treat any ingestion as an emergency.
Toxicity in cats is less documented but suspected — keep grapes and raisins completely away.
Tartaric acid (the likely toxin) damages kidneys. Sensitivity varies wildly and unpredictably between dogs.
Vomiting within hours, lethargy, loss of appetite, reduced or absent urination.
Call your vet or poison control immediately — even for one grape. Do not wait for symptoms.
ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661 — 24/7, a fee may apply. Your own vet first when reachable.