Can dogs eat grapes?

Why

Grapes belong to a small group of everyday foods that are genuinely dangerous to dogs rather than just unwise. The leading explanation is tartaric acid and its salt, potassium bitartrate, which grapes contain in unusually high amounts and which dogs appear to handle very poorly. The precise mechanism is still being worked out, but the effect itself is not in doubt: grapes damage the kidneys, and they can do it fast.

What happens inside the dog is injury to the tiny filtering tubules of the kidneys — acute kidney injury. The first outward sign is usually vomiting within a few hours, but the damage can be quietly underway before a dog looks unwell at all. As the kidneys struggle, waste builds up in the blood, and in the worst cases they stop producing urine altogether. This is exactly why waiting to see whether your dog gets ill is the wrong move: by the time it is obvious, the window in which a vet can help most has often closed.

The hardest part for owners to accept is that sensitivity varies wildly between individual dogs, and we cannot predict who is vulnerable. Some dogs hoover up a handful and are completely fine. Others become seriously ill after very little. It does not track reliably with breed, size, age or how healthy the dog is, and — importantly — a dog who has eaten grapes before without any trouble is not protected next time. Past luck tells you nothing about this time.

Dried grapes deserve their own warning. Raisins, sultanas and currants are the same problem concentrated, so a dog can swallow a great many in one small mouthful, and they hide inside food we do not think of as grapes at all. Grape juice, grape must and cream of tartar (which is potassium bitartrate) sit in the same family of concern and are best kept away from dogs too.

Is any amount safe?

There is no safe amount, and this is not caution for caution's sake — it is because no reliable threshold exists to give you. Vets cannot tell you that a certain number of grapes is fine for a dog of a certain weight, because the dose that badly hurts one dog may pass through another of the same size with no effect at all. That unpredictability is the whole danger: guessing means gambling with an organ that does not grow back. Treat every grape, raisin, sultana and currant as off the menu, in every form, at every size of dog, including the one your neighbour swears is "just a treat".

Signs to watch for

• Vomiting, often within a few hours of eating them, sometimes with bits of grape or raisin visible
• Going quiet and unusually tired, or turning her nose up at food she normally loves
• Diarrhoea, and sometimes a tummy that seems tender or sore when touched
• Drinking noticeably more than usual and asking to go out to wee more often
• Then the opposite — straining, producing very little urine, or none at all, which is a serious warning sign
• Breath that smells odd, faintly chemical or like ammonia

Keeping it out of reach

• Learn where they hide: flapjacks, cereal bars, malt loaf, scones, hot cross buns, mince pies, Christmas pudding, stollen, trail mix, granola, and some curries, tagines and salads all commonly contain raisins or sultanas.
• Brief everyone in the house, especially children and visiting relatives, that one grape is not a kind treat. Most cases start with someone who genuinely meant well.
• Mind the floor and the worktops — dropped raisins are small, sticky and easy for a dog to find first. Keep lunchboxes, fruit bowls and shopping bags above nose height, and use a bin your dog cannot open.
• As a precaution, keep cream of tartar out of reach too, including homemade playdough made with it, and offer safe treats like a little carrot or apple (no pips) when you want to share something.

Common questions