Grapes & Raisins poisoning in dogs and cats
Toxic agent: Suspected tartaric acid and potassium bitartrate · Reviewed 2026-08-18
Phone a vet now, before reading on. Have ready: your pet's weight, roughly how much was eaten and when, and the packaging if there is any. ASPCA Animal Poison Control (+1 888 426 4435), Pet Poison Helpline, or Animal PoisonLine in the UK.
Grapes and raisins cause acute kidney failure in dogs, and uniquely among common poisons there is no dose anyone can call safe — some dogs eat a bunch with no effect, others go into renal failure on a handful.
What it actually does
For decades the toxic principle was unknown, which is why the advice was always maximally cautious. Tartaric acid and its salt potassium bitartrate are now the leading candidates, which fits both the grape family and the observation that dogs are unusually sensitive to tartaric acid. The kidney damage is acute tubular necrosis — the filtering tubules die.
How much matters
This is the entry where a dose table would be misleading, so there isn't one. What is documented:
| Reported toxic amounts | as little as 4–5 grapes in a small dog, and no effect at all in other dogs eating far more |
|---|---|
| Raisins and sultanas | more concentrated by weight than fresh grapes, so a smaller volume matters |
| Seedless, organic, peeled, cooked | no difference — none of these change the outcome |
Because susceptibility appears idiosyncratic, veterinary practice is to treat every ingestion as significant rather than to calculate. That is genuinely different from chocolate, where the maths is meaningful.
What you will see, and when
Onset: Vomiting within 6–12 hours; kidney values rise over 24–72 hours. Typical course: Kidney monitoring for at least 72 hours.
- 6–12 hoursVomiting, sometimes with grape or raisin fragments visible, then lethargy and loss of appetite
- 24 hoursAbdominal pain, more vomiting, diarrhoea, dehydration
- 48–72 hoursFalling urine output, then no urine at all — the point at which the outlook turns poor
What the vet will do
Decontamination if the ingestion is recent, then aggressive intravenous fluids to protect the kidneys, with blood urea nitrogen, creatinine and urine output tracked for three days. Dialysis is occasionally used where available. There is no antidote.
Outlook
Good if fluids start before kidney values move. Poor once the dog stops producing urine.
Dogs and cats are not the same here
Well documented in dogs. Cats and ferrets are theoretically at risk but cases are scarce, most likely because they do not eat fruit voluntarily rather than because they are protected.
Where it comes from in a normal house
- Fresh grapes and sultanas
- Raisin bread, hot cross buns, fruitcake, mince pies
- Trail mix and cereal bars
- Chocolate-covered raisins, which pair this with theobromine
- Grape juice and wine
The thing people get wrong
“My dog ate grapes once and was fine, so grapes are fine for my dog.”
Sensitivity varies between individuals and, as far as anyone can tell, between exposures. A tolerated dose on Tuesday is not a guarantee for Friday. This is the specific reason the profession does not calculate a threshold for grapes.
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How much Grapes & Raisins is dangerous?
Because susceptibility appears idiosyncratic, veterinary practice is to treat every ingestion as significant rather than to calculate. That is genuinely different from chocolate, where the maths is meaningful.
How long after exposure to Grapes & Raisins do symptoms start?
Vomiting within 6–12 hours; kidney values rise over 24–72 hours. Vomiting, sometimes with grape or raisin fragments visible, then lethargy and loss of appetite. Kidney monitoring for at least 72 hours.
Is Grapes & Raisins worse for cats or dogs?
Well documented in dogs. Cats and ferrets are theoretically at risk but cases are scarce, most likely because they do not eat fruit voluntarily rather than because they are protected.
Is it true that: My dog ate grapes once and was fine, so grapes are fine for my dog.
Sensitivity varies between individuals and, as far as anyone can tell, between exposures. A tolerated dose on Tuesday is not a guarantee for Friday. This is the specific reason the profession does not calculate a threshold for grapes.
Related emergencies
Sources
This page is information, not veterinary advice. Toxic doses vary with body weight, age, breed and individual sensitivity, and the figures above exist to explain what a vet is assessing, never to decide that an amount is safe. If you are reading this because something has already been eaten, call a vet.