Short answer: Grapes, raisins, currants, and sultanas are treated as toxic to cats on a precautionary basis — KibbleIQ rates them F. They cause acute kidney injury in dogs, and poison-control bodies advise treating them as potentially toxic to cats as well (VCA Animal Hospitals; Pet Poison Helpline). The honest picture matters here: documented cases are overwhelmingly in dogs, and there are no published case reports in cats — only anecdotal reports of kidney failure in cats and ferrets (Merck Veterinary Manual). Because cats are highly susceptible to kidney injury and the true risk is unknown, the recommendation is to avoid grapes and raisins entirely, with no established safe amount (VCA Animal Hospitals; Pet Poison Helpline). The leading hypothesis for the dog toxin is tartaric acid and its salt potassium bitartrate (ASPCA Animal Poison Control Center). If your cat eats any amount, contact a poison-control hotline or your vet promptly rather than waiting for symptoms.

Why grapes are treated as toxic to cats

In dogs, grapes, raisins, currants, and sultanas can cause acute kidney injury, sometimes after surprisingly small amounts (Merck Veterinary Manual; Cornell University Riney Canine Health Center). For years the responsible toxin was unknown; the leading hypothesis now is tartaric acid and its salt, potassium bitartrate (ASPCA Animal Poison Control Center; Cornell University Riney Canine Health Center). The proposed mechanism is that dogs poorly excrete organic acids, allowing tartaric acid to accumulate in the kidney’s proximal tubular cells and damage them (Merck Veterinary Manual).

Here is the honest nuance that defines this question. Almost all documented cases are in dogs. The Merck Veterinary Manual states plainly that anecdotal reports exist of renal failure in cats and ferrets after ingesting grapes or raisins, although there are no published case reports in these species (Merck Veterinary Manual). VCA Animal Hospitals likewise says it is unknown whether grapes, raisins, and currants cause the same poisoning in cats as in dogs — but because cats are so sensitive to kidney injury, VCA recommends avoiding these fruits entirely and contacting a poison hotline or your vet after any exposure (VCA Animal Hospitals). Pet Poison Helpline has added grapes to its list of top feline poisons and advises that any ingestion be treated as potentially toxic (Pet Poison Helpline). So the F grade rests on caution, not on a large body of feline cases — the canine evidence is far stronger than the feline evidence, and we will not pretend otherwise.

How much grape or raisin is dangerous for a cat

There is no established safe amount for cats, and there is no reliably established toxic amount either. Pet Poison Helpline states there is no well-established toxic dose and that even a small amount can be a concern, advising that any ingestion be treated as potentially toxic (Pet Poison Helpline). The reaction is notoriously unpredictable even in dogs: tartaric acid concentration varies widely between grapes, and individual sensitivity differs, so any ingestion should be treated as potentially toxic (Cornell University Riney Canine Health Center; ASPCA Animal Poison Control Center). Because the feline data is thin, no one can responsibly publish a safe number of grapes for a cat — so the only safe number is zero.

Cats are obligate carnivores that lack the ability to taste sweetness, so most are simply indifferent to grapes and raisins, which makes deliberate grape-eating uncommon (Cornell Feline Health Center). The real-world risk is usually hidden raisins rather than fresh grapes. Raisins, currants, and sultanas turn up baked into cookies, breads, scones, granola, trail mix, and holiday foods — and a curious cat may swallow one while investigating a dropped snack. Treat dried fruit as the higher concern: raisins are more concentrated than fresh grapes, so a small raisin can carry more tartaric acid than its size suggests (Cornell University Riney Canine Health Center).

Symptoms of grape or raisin poisoning

The pattern of concern is acute kidney injury, extrapolated largely from dogs. The earliest sign is typically vomiting (often within 6 to 12 hours), sometimes with diarrhea, followed by lethargy, decreased appetite, abdominal pain, weakness, and dehydration (Merck Veterinary Manual). As the kidneys are affected, you may see changes in thirst and urination — increased at first, then decreased or absent urination as kidney function fails, which is a medical emergency (Cornell University Riney Canine Health Center; Merck Veterinary Manual). In dogs, kidney failure can progress within roughly 24 to 72 hours of ingestion (Merck Veterinary Manual). Because these signs are nonspecific and can appear after the best treatment window has passed, do not wait for symptoms before acting.

What to do if your cat ate grapes or raisins

Act promptly — do not adopt a wait-and-see approach. If you know or suspect your cat ate any grapes, raisins, currants, or sultanas (including inside a cookie or other baked good), contact the ASPCA Animal Poison Control Center at 1-888-426-4435, Pet Poison Helpline at 1-855-764-7661, or your veterinarian or nearest emergency clinic right away (ASPCA Animal Poison Control Center; Pet Poison Helpline; VCA Animal Hospitals). Have details ready: roughly how much, whether fresh or dried, and when it happened.

Early decontamination matters. There is no antidote for grape or raisin toxicity, so treatment relies on early intervention and supportive care for the kidneys, which is most effective when started before kidney injury sets in (Pet Poison Helpline). Your vet or the poison center may advise inducing vomiting and starting intravenous fluids to protect the kidneys, with blood tests to monitor kidney values (Merck Veterinary Manual; VCA Animal Hospitals). Do not try to make your cat vomit at home unless a veterinary professional directs you to — let the experts guide the steps.

Frequently asked questions

Are grapes definitely toxic to cats, or just dogs?

The clearest answer is honest uncertainty. Grape and raisin kidney injury is well-documented in dogs, but in cats the evidence is limited — the Merck Veterinary Manual notes only anecdotal reports of kidney failure in cats and ferrets, with no published feline case reports (Merck Veterinary Manual). VCA Animal Hospitals states it is unknown whether these fruits cause the same poisoning in cats, yet still recommends avoiding them because cats are so prone to kidney injury (VCA Animal Hospitals). Pet Poison Helpline goes further and lists grapes among its top feline poisons, advising that any ingestion be treated as potentially toxic (Pet Poison Helpline). So: not proven the way it is in dogs, but treated as toxic on a precautionary basis — which is why we keep the food off the menu entirely.

What about raisins, currants, or sultanas?

Treat all of them as the same hazard, or worse. Grapes, raisins, Zante currants, and sultanas are all included in the toxicity concern because they share the suspected toxin, tartaric acid (Cornell University Riney Canine Health Center). Dried forms — raisins, sultanas, and currants — are more concentrated than fresh grapes, so a small piece can deliver a disproportionate amount of tartaric acid (Cornell University Riney Canine Health Center). The dried-fruit currant (a small raisin) is the relevant hazard here, not the unrelated fresh black or red currant berries. As with grapes, there is no established safe amount, so none of these should be given to a cat (Pet Poison Helpline).

My cat ate a raisin from a cookie — should I worry?

Don’t panic, but don’t ignore it either — call for advice rather than guessing. Because there is no reliably established toxic dose and the reaction is unpredictable even in dogs, poison-control guidance is to treat any ingestion as potentially toxic rather than assume a single raisin is harmless (Pet Poison Helpline; Cornell University Riney Canine Health Center). Contact the ASPCA Animal Poison Control Center at 1-888-426-4435 or Pet Poison Helpline at 1-855-764-7661, or your vet, and tell them how much your cat ate and when. They can weigh the specifics — including any chocolate or other toxic ingredients in the cookie — and tell you whether monitoring at home or a vet visit is warranted. Acting early is far better than waiting for signs to appear.

For related context, see our Can Cats Eat Chocolate? and Best Cat Food for Kidney Disease. To check whether your cat’s food contains any of these ingredients, paste the ingredient list into the KibbleIQ analyzer. For methodology context, see our published methodology.