Poisoning guide
Grapes and raisins: the toxin with no safe dose
One grape can be enough. Or a handful might do nothing. That unpredictability is exactly why every exposure is treated as an emergency.
The short version
- There is no safe dose. Kidney failure has been reported after a single grape in a small dog, and after large handfuls in a large one.
- Raisins are worse. Drying concentrates the toxin roughly four-fold by weight.
- Timeline: vomiting within hours, then a quiet 24–72 hour window in which kidney damage develops with few visible signs.
- Treatment works best early: decontamination within two hours, then 48 hours of aggressive intravenous fluids.
- Do not wait for symptoms. By the time a dog is urinating less, kidney injury is already established.
Why nobody can tell you a safe number of grapes
Most poisonings have a dose-response curve: more toxin, more risk, with a threshold below which nothing happens. Grapes do not behave that way. Veterinary poison centres have recorded kidney failure after a single grape in a 3 kg dog and after a handful in a 25 kg dog, with no consistent relationship between dose and outcome.
The likely culprit is tartaric acid, identified in 2021 as the compound responsible for grape and raisin toxicity in dogs. Dogs appear to lack an efficient way to metabolise it, and in susceptible individuals it produces acute tubular necrosis — direct damage to the cells that filter blood. But susceptibility varies enormously between individual dogs, which explains the frustrating pattern where one dog eats raisins and is fine while another is hospitalised.
That variability is exactly why veterinary guidance is unanimous: treat every exposure as potentially serious. "My last dog ate grapes and lived to sixteen" is not evidence about this dog.
Grapes, raisins, sultanas, currants — all the same problem
| Product | Risk | Where it hides |
|---|---|---|
| Fresh grapes | High | Fruit bowls, lunch boxes, picnic blankets, children's hands |
| Raisins / sultanas | Very high — concentrated | Trail mix, cereal, cookies, Christmas pudding, mince pies, granola |
| Currants | Very high | Baked goods, jams, savoury sauces |
| Grape juice / wine | High | Juice cartons, spilled glasses, ice lollies |
| Raisin-containing bread | High | Fruit loaf, hot cross buns, panettone |
The hiding places matter more than the fruit bowl. Most raisin exposures we see described involve baked goods, and the owner often did not think of the cake as "fruit" at all. A single mince pie can contain 30–40 g of raisins — a substantial dose for a medium dog.
The 72-hour window
Grape toxicity is a waiting game that you should not play at home. The clinical pattern is:
- 0–6 hours: vomiting, sometimes diarrhoea, lethargy, loss of appetite. Many dogs show nothing at all.
- 12–24 hours: increased thirst and urination as the kidneys struggle to concentrate urine. This is easy to miss.
- 24–72 hours: urine output drops sharply or stops entirely. Vomiting returns, the dog becomes depressed, and bloodwork shows rising creatinine and urea.
Once a dog stops producing urine, the prognosis becomes guarded and dialysis or euthanasia may be the only options. Everything that helps happens before that point.
What a vet will do
Treatment is not complicated, but it is time-critical and it happens in hospital, not at home.
- Decontamination
If the grapes were eaten within about two hours, induce vomiting and give activated charcoal to reduce absorption.
- Baseline bloodwork
Creatinine, urea, electrolytes and a urine specific gravity, so there is a reference point to compare against.
- 48 hours of intravenous fluids
Aggressive fluid therapy is the core of treatment. It maintains urine flow and keeps the tubules perfused while the toxin is cleared. Most vets admit the dog for at least two days.
- Repeat bloodwork at 48–72 hours
If kidney values are normal at that point, the dog is usually out of danger.
The cost of two days of fluids is real, and it is still far less than the cost of dialysis — or the alternative. If you are deciding whether to "watch and see", this is the calculation to make.
The most common and most dangerous mistake with grapes is waiting to see whether anything happens. Because damage accumulates silently, a dog that looks normal at hour twelve may already have irreversible injury.
Raisins, sultanas, currants, grape juice, wine and raisin bread all carry the same risk. So do some grape-derived supplements and vinegars, though the risk there is far lower. When in doubt, exclude.