Grapes and raisins seem like an innocuous snack, but for dogs can actually be deadly. This discovery was not made until the early 2000’s. Unfortunately we still don’t completely understand why grapes and raisins can wreak such havoc on the canine kidney. Just a few grapes or raisins can shut down a dog’s kidney function. However, what’s interesting , is that grapes are not toxic to all dogs. Not every dog will develop severe consequences after eating this fruit. Kidney failure after eating grapes/raisin is considered idiosyncratic in dogs. Grapes, raisins, sultanas and Zante currants (which are actually a raisin) are all members of the species Vitis vinifera. All of these members of the Vitis vinifera species can cause toxicity when ingested by a dog. Read on to learn how many grapes are toxic to dogs and how to treat to prevent kidney failure in your dog!
The most current research suggests that tartaric acid in the grape is what is responsible for the toxic effects. The amount of tartaric acid can vary depending on the type of grape, how they are grown, and how ripe they are. Sources of grapes/raisin toxicity are not only due to ingestion of the whole fruit. Composted grapes and ingestion of grape marc (seeds, skins, and stems of grapes used in wine production) laid down as fertilizer are also sources reported in the literature.
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Are sea grapes toxic to dogs? What about grape seed extract, grapeseed oil, grape jelly, grape juice and wine?
Sea grapes are not members of Vitis vinifera , but are of the species Coccoloba uvifera. Sea grapes are not toxic to dogs and are not listed on the ASPCA poisonous plant list for dogs. Interestingly, grape seed extract, grapeseed oil and grape jelly, grape juice, and wine have not been found to cause kidney damage.
Dogs are the only species reported to be susceptible to kidney damage from grape ingestion.There have been no breed, age or gender predispositions in regards to the kidney toxic effects of grapes and raisins in dogs. There may be some anecdotal reports of cats sustaining kidney damage from the fruit, but nothing is substantiated yet.
Can eating one grape be toxic to a dog? How many grapes are toxic to a dog?
The lowest documented doses of grapes are 0.7 oz/kg (19.6g/kg) and 0.11 oz /kg of raisins (2.8g/kg), however, lower amounts may actually still be dangerous to some dogs. The chart below is based on an assumed toxic dose of : 19.6grams/kg of grapes and 2.8g/kg of raisins as toxic. As you can see, if you have a small, 5 lb dog, it can take only 13 raisins to cause kidney failure. Assuming an average weight of about 5 grams per grape, a dog would have to weigh only 5 pounds or less to have a single grape come close to a toxic dose.
| Weight lbs/kgs | Toxic dose grapes | Number of grapes | Toxic dose raisins | Number of raisins |
| 5 pounds / 2.3 kg | 45 grams/0.1lbs | 9 | 6.4 grams | 13 raisins |
| 10 pounds/ 4.5 kg | 88 grams/0.2lbs | 17 | 13 grams | 26 raisins |
| 20 pounds / 9.1 kg | 178 grams/0.4lbs | 36 | 26 grams | 52 raisins |
| 30 pounds/ 13.6 kg | 267 grams/0.6lbs | 53 | 38 grams | 76 raisins |
| 40 pounds/ 18.1 kg | 355 grams/ 0.8lbs | 71 | 51 grams | 102 raisins |
| 50 pounds/ 22.7 kg | 445 grams/ 1lb | 89 | 64 grams | 128 raisins |
| 60 pounds/ 27.2 kg | 533 grams/1.2 lbs | 107 | 76 grams | 152 raisins |
| 70 pounds/ 31.8 kg | 623grams/1.4lbs | 125 | 89 grams | 178 raisins |
| 80 pounds/ 36.4 kg | 713 grams/ 1.6 lbs | 143 | 102 grams | 204 raisins |
Using lowest published toxic dose of grapes 19.6 g/kg and raisins 2.8g/kg
Survival rate for dogs who ingest grapes or raisins
Multiple studies in the past have shown a 50% survival rate for dogs that get sick following grape/raisin ingestion. However, a new retrospective study of dogs following grape and raisin ingestion found a much more positive outlook for these patients. Of the 139 dogs who ingested grapes/raisins, the incidence of acute kidney injury was low at only 6.7% of dogs! In addition, the rate of mortality was very low.
Compared to previous studies of dogs, most of the dogs exposed to grapes and raisins in this recent study (88%) were “decontaminated” by inducing vomiting and providing activated charcoal to bind up toxins remaining in the GI tract. In previous studies showing a 50% mortality rate only one dog of 168 studied received this type of “decontamination “ treatment. There is an increased risk of mortality noted in dogs that received treatment later following the development of symptoms. There is a decreased risk of developing acute kidney injury if medical treatment is provided promptly and if decontamination procedures are provided.
How long after eating grapes will a dog get sick?
The symptoms of kidney failure in a dog from grape and raisin ingestion begin quickly, within a few hours of ingestion. In nearly all reported cases, vomiting is a symptom. Sometimes, this is how an owner discovers the ingestion: when they see evidence of grapes or raisins in the vomitus.
Within 24 hours diarrhea, a sharp decline in appetite, abdominal pain, hypersalivation/nausea and lethargy can develop.
Less frequent symptoms observed are: edema (puffy extremities), hypersalivation, high blood pressure, trembling, seizures and incoordination
Within 1-5 days signs of increased thirst, urination, incoordination, weakness, edema of the legs and trembling can develop. As kidney disease progresses, the ability to produce urine may be compromised in nearly 50% of dogs. This means there may be a sharp reduction in urine produced or complete failure to be able to produce any urine.
How quickly will there be abnormalities detected in blood work following grape/raisin ingestion in dogs?
Elevated kidney enzymes can be noted in lab tests within 2 days of ingestion. Serum creatinine begins to rise more quickly after exposure and BUN takes a little longer: generally about 24 hours later. Calcium and phosphorus values may rise as well, but this is not always a consistent finding. Other serum biochemistry abnormalities that can develop are elevated liver enzymes ALT and ALP as well as increased or decreased in potassium.
In later stages of toxicity, anemia and low platelet counts may be seen on the complete blood count. A urinalysis may show dilute urine, protein loss, crystals and casts (sloughing of the renal tubules).
Wobbliness and incoordination can be a feature of grape toxicity in dogs
Neurologic symptoms of incoordination/wobbliness, trembling and seizures are a unique feature of kidney injury with grape and raisin toxicosis. The median onset of wobbliness and incoordination occurs about 2 days after ingestion and in the studies has been associated with a worse prognosis for recovery. Occasionally, dogs who ingest grapes or raisins may develop severe neurologic abnormalities which can obscure the diagnosis. This is because it is an infrequent symptom of dogs who suffer acute kidney injury.
One recent study did report a 50% survival in dogs with neurologic symptoms from grape/raisin ingestion and a little less than half of the dogs with neurologic symptoms made a full neurologic recovery.
The presence of neurological signs (although still uncommon in grape and raisin toxicity) may be an important feature to help distinguish grape and raisin toxicity from other causes of acute renal failure. These signs may dominate the clinical picture of a patient even before kidney values rise.
Other causes of acute renal failure that can cause neurologic abnormalities are : leptospirosis infection and ethylene glycol toxicity. Leptospirosis infection frequently causes elevated liver values and is to produce neurologic abnormalities. Ethylene glycol toxicity produces characteristic abnormalities detected by imaging the kidneys with ultrasound and also produces characteristic crystals in the urine.
Initial treatment for grape toxciity
If the ingestion was recent (within the past 4 hours) and the dog has not vomited, then inducing vomiting is recommended. Although the stomach can empty it’s contents within 1-2 hours, sometimes there is delayed gastric emptying and there may be grapes or raisins that can be removed by inducing vomiting. There have been dogs documented to have vomited up grapes/raisins as long as 12 hours post ingestion!
Even if your dog has vomited up grapes and/or raisins, it is still recommended to provide additional treatment (typically activated charcoal and then fluid therapy). This is because vomiting generally only brings up about 40-60% of the contents of the stomach.
Activated charcoal is an inert material that is highly porous and can absorb many types of toxic compounds present in the GI tract. For large ingestions, a second dose of activated charcoal is often provided 8-12 hours later. Although this procedure is recommended, and likely does provide benefit, it is important to note that there have been studies proving efficacy for this treatment in grape/raisin toxicosis.
Hospital therapy after eating grapes or raisins
Additional supportive treatment can be provided by admitting a patient for IV fluid therapy to help flush the kidneys. The recommended length of time is a minimum of 48 to 72 hours of fluid therapy. Dogs treated in the hospital are provided anti nausea medication, antacid therapy, nutritional support and close monitoring of their electrolyte and kidney values. Urine output and fluid rates are adjusted accordingly.
Any dog that is hospitalized but worsening after 12-24 hours of therapy should be considered for hemodialysis if possible. Any dog that develops oliguria (decreased urine production) or anuria (inability to produce urine) have a very poor prognosis.
Average hospital stay for a dog with grape or raisin toxicity
In a study of 139 cases of grape/raisin ingestion in dogs, the median hospitalization length for dogs presenting within 4 hours of ingestion was 24 hours. The median hospitalization length for dogs presenting more than 4 hours after ingestion was 36 hours.
An interesting feature of this study was that not all dogs that presented with clinical symptoms (such as vomiting) developed acute kidney injury following their ingestion. Similarly, some dogs that had no clinical signs after ingestion developed acute kidney injury.
Other causes of acute kidney injury in dogs
Acute kidney injury in dogs is defined as an abrupt decline in kidney filtration characterized by elevated kidney values : creatinine and BUN and changes in urine production (increased or decreased). The most common reported causes of acute kidney injury in dogs are: abrupt changes in blood flow to the kidneys (low blood pressure, blood loss), infections (leptospirosis and ascending urinary tract infections), toxin exposure , and obstruction of the urinary tract. A large meta-analysis of AKI in dogs and cats did show that acute kidney injury due to non-infectious causes carried a higher rate of mortality.
All causes of acute kidney injury in dogs
- Isolated ischemic events (decreases in blood flow) such as from : pancreatitis, cardiovascular shock, sepsis, deep anesthesia, liver failure, hyperthermia, severely low albumin levels, or clots to the kidney
- Kidney toxins such as: ethylene glycol, cisplatin, aminoglycosides, calcium, thiacetarsamide, TMS antibiotic, captopril, non-steroidal anti-inflammatories, grapes/raisins
- Infections: Leptospirosis and pyelonephritis
- Cancer of the kidney : lymphoma
- Multiple systemic disorders
Summary : grape and raisin induced kidney failure in dogs
Tartaric acid has been identified as the most likely toxic principle in grapes/raisins. As far as we know, Dogs are the main species susceptible to acute kidney injury from grapes and raisins. Kidney failure from ingestion of grapes and raisins in dogs is still considered likely idiosyncratic. Not all dogs that ingest the same amount of grapes or raisins will suffer from kidney injury. A single grape is unlikely to trigger kidney injury unless the dog is under 5 lbs. However, fewer raisins are needed to cause kidney injury and as few as 13 raisins can induce kidney injury in a 5 lb dog.
Prompt treatment (within 4 hours) of any dog who has ingested grapes or raisins provides the best chance at full recovery. Initial treatment focuses on prompt decontamination by inducing vomiting and then providing activated charcoal to bind toxins left in the GI tract. Intravenous fluid therapy support for 48 to 72 hours is also recommended to provide the best chance at a full recovery.
