Ask Dr. T: My Dog Ate One Grape–Should I Worry?

“Hi, how are you? Did you know you’re my emergency vet?”

I was sitting at home on a recent evening when my sister-in-law called about one of their Boston Terriers. 

She explained, “My dog ate one grape a couple of minutes ago. Should I be worried? What should I do?”

She knew dogs are not supposed to eat grapes, but she wasn’t sure if one single grape could make him sick. 

Can One Grape Kill a Dog?

The current standard of veterinary care dictates that any quantity of grape or raisin ingestion by a dog should be taken very seriously. There are multiple reports of dogs going into renal failure after eating even small amounts of the forbidden fruit. 

Since Ollie had just eaten a grape a few minutes before she called me, the best immediate plan was to try to get him to vomit by giving him hydrogen peroxide (H2O2).

I told her to check to make sure her peroxide was fresh by pouring a little bit in the sink and listening for a “sizzle” sound when it hit the drain. No sizzle=stale hydrogen peroxide that won’t make a dog vomit. 

I told her to give her pup a little treat to eat right before giving him the calculated dose of H2O2. Then she could walk him around a bit to help induce vomiting. 

IMPORTANT: Before you induce your dog to vomit, it’s a good idea to check with a vet first. Some toxins can cause more damage if a dog vomits them up. 

Try calling your regular vet or nearby emergency vet clinic if it’s after hours for help. You can also call the number below 24 hours a day for help with toxin ingestion.

There is a fee for the service ($75 at the time of publication), but the advice you’ll get could save your pet’s life. You’d think I get a commission for recommending them so much (haha) but I don’t. I just dearly love the service they provide! CALL 

Call Pet Poison Helpline (855) 764-7661

My sister-in-law immediately gave Ollie the H2O2 and after looking unhappy for a couple of minutes, he vomited up the grape! Here it is…

If he hadn’t vomited within about 20 minutes, I was going to advise her to take him to the emergency vet clinic. They have a more powerful drug that works in almost every case to induce vomiting.

But a dog’s stomach may start to digest the grape within an hour, so it’s really important not to waste time trying to get your dog to vomit at home. 

Remember that although H2O2 is safe to give in small quantities, it can be very irritating to the stomach and esophagus lining. Don’t keep giving repeat doses! Just go to the emergency clinic for help from a vet. 

Even though he vomited up the grape he ate, Ollie still visited his veterinarian to have an exam and lab tests to check for kidney-related abnormalities.

Thanks to his owner’s quick action, he came through this challenge in good shape.

Seriously, How Can One Grape Hurt a Dog?

Scientists have yet to settle on what the toxic component is. A report from veterinary toxicologists in 2021 proposed it may be tartaric acid and potassium bitartrate.(1)

Dogs have a uniquely high absorption rate of these compounds and excrete them via their kidneys.(4) 

The reaction to grape toxicity in dogs is severe damage to kidney tissue. We don’t know why some dogs are so sensitive to eating grapes while other dogs eat grapes with no ill effect. 

It doesn’t take much of the fruit to cause problems for dogs, either, as I will discuss below.

What If Your Dog Eats Raisin Bagels, Grape Juice, Etc.?

Anything that contains grapes, raisins, sultanas (light-colored raisins), or Zante currants has the potential to cause a toxic reaction in dogs.

It is believed that only the fruit of the Vitis plant is toxic, but it’s best to avoid letting your dog eat any part of a grape plant.

ANY food that contains grapes, raisins or currants could be harmful to your dog. That includes bagels, cookies, trail mix, breakfast cereal, granola bars, and salad with grapes as an ingredient. 

When it comes to dogs ingesting grape juice, juice beverages containing grape juice, grape jam/jelly, grape seed extract and wine, veterinary toxicologists say there are no reports of toxicosis.

I still don’t recommend letting your dog eat any of these things because our understanding of their effect on dogs is incomplete.

Any ingestion of fresh or dehydrated purple, red, white, seeded or seedless grapes, raisins or currants should be considered possibly toxic to dogs. 

How Many Grapes Does It Take to Make a Dog Sick?

I wouldn’t take a chance on letting your dog eat any amount of grapes. There is a great deal of variability in the toxic response to grapes and raisins in dogs. 

We do not know the MINIMUM toxic dose of grapes/raisins in dogs.

There are reports of dogs getting seriously ill after ingesting as little as 0.7 ounces (20 grams) of GRAPES per kilogram of body weight. An average grape weighs about 0.18 ounces (5 grams).

And only 0.11 ounces (3 grams) of RAISINS per kilogram of body weight have caused toxic reactions in dogs. A snack-size box of raisins usually contains 1 ounce of raisins.

Here’s how that looks for different sizes of dogs in English measurements:

Dog’s Weight in Pounds	Ounces of Grapes	Ounces of Raisins
10	3.2	0.5
20	6.4	1
30	9.6	1.5
40	12.7	2
50	16	2.5

Please note that even smaller amounts of grapes/raisins can make dogs sick. We don’t know the MINIMUM amount of grapes/raisins that can cause kidney problems in dogs. 

If you’re looking for a grape toxicity calculator, you’re thinking about the situation the wrong way!

It’s impossible to predict how an individual dog will react to eating grapes or raisins, so experts advise you to prepare for the worst possible outcome in all cases and take action immediately.

Besides, unless you watch your dog every second, he could’ve eaten more grapes/raisins than you think. Don’t chance it–consult your veterinarian and take their advice on treatment.

What Will Happen If a Dog Eats Grapes?

The toxic effect of grapes acts on a dog’s kidneys. Tissue samples from affected dogs show destruction of renal tubules which are important for maintaining the body’s water and electrolyte balance. 

Dogs with significant damage to their renal tissue suffer from acute kidney failure. When the kidneys stop working, excess water and waste products build up in the dog’s blood and body. Unless a dog gets aggressive treatment, they become very sick and often dies. 

One tiny morsel of good news is that dogs with acute kidney failure from grape toxicosis can survive and have their kidneys heal.

In one study, 53% of dogs who were hospitalized for grape-related kidney injury survived. (2) But it often requires weeks of treatment and can be a very expensive undertaking.

How Long Before a Dog Gets Sick After Eating Grapes/Raisins?

Toxic damage to the kidneys starts to occur quickly after eating grapes/raisins.

Although most dogs who suffer from grape toxicity vomit within 24 hours after eating the fruit, you may not notice symptoms of serious problems until a day or so later.   

Signs of kidney failure become apparent within 1-5 days after a dog eats grapes.

Symptoms may include increased drinking, body swelling, trembling, weakness, decreased or increased urine production and nausea. Blood tests show signs of kidney failure including increased BUN and creatinine.

What If My Dog Ate Grapes/Raisins a Week Ago?

If your dog ate grapes/raisins more than a few hours ago, treatment can still help him survive so call the vet!

Clients have asked me “What if my dog ate grapes two weeks ago and he seems fine?” If your dog seems normal in every way this much later, she probably is fine.

But I still recommend you have a vet check her out for subtle changes that may be significant. 

What to Do If Your Dog Eats Grapes, Raisins or Currants

If your dog already ate a grape, raisin, currant or a food containing one of these, you need to move quickly. 

1. Estimate when your dog ate the food and how much he ate. 
2. Take note of any unusual symptoms he has.
3. Call your veterinarian for help immediately. If it’s after-hours call an emergency vet clinic or the helpline listed above and below in this article. They can advise you on whether you should induce vomiting at home or bring your dog to the clinic.
4. If your dog is vomiting or showing any signs of distress, transport him to a veterinary clinic right away. 

Treatment for Dogs Who Eat Grapes

Veterinary toxicologists recommend treatment for dogs who eat grapes and raisins in all cases, no matter the amount eaten. Your veterinarian will help you decide the right treatment for your unique dog.

The basic treatments you can expect include:

• Hospitalization for treatment and monitoring for a minimum of 48 hours
• Decontamination of dog’s stomach (induce vomiting)
• Administer activated charcoal
• Check baseline blood tests for BUN, creatinine, calcium, etc.
• Check baseline urinalysis
• Intravenous fluid administration

Dogs with significant kidney damage may require additional treatment and may need to stay in the hospital longer. 

The most important treatment is early decontamination. If your dog just ate a grape or 20 of them, you need to get them out A.S.A.P.

Call your vet, a veterinary emergency clinic or the helpline number below for instructions on how to do this. 

Summary

Grapes, raisins and currants can cause severe kidney damage when eaten by dogs. It doesn’t happen in every dog, but it’s impossible to predict the outcome after a dog eats the fruit.

We don’t know the minimum amount of grapes, raisins or currants that can cause kidney injury in dogs.

Veterinary toxicologists recommend aggressive treatment for dogs who have eaten any amount of grapes, raisins or currants. Call your veterinarian, veterinary emergency clinic or 

Call Pet Poison Helpline (855) 764-7661

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References

1. . (2021). Letters to the Editor, Journal of the American Veterinary Medical Association, 258(7), 704-707. Retrieved Jul 12, 2022, from https://avmajournals.avma.org/view/journals/javma/258/7/javma.258.7.704.xml
2. Eubig, P. A., Brady, M. S., Gwaltney-Brant, S. M., Khan, S. A., Mazzaferro, E. M., & Morrow, C. M. (2005). Acute renal failure in dogs after the ingestion of grapes or raisins: a retrospective evaluation of 43 dogs (1992–2002). Journal of veterinary internal medicine, 19(5), 663-674.
3. Schweighauser, A., Henke, D., Oevermann, A., Gurtner, C., & Francey, T. (2020). Toxicosis with grapes or raisins causing acute kidney injury and neurological signs in dogs. Journal of veterinary internal medicine, 34(5), 1957–1966. https://doi.org/10.1111/jvim.15884
4. Spiller, G. A., Story, J. A., Furumoto, E. J., Chezem, J. C., & Spiller, M. (2003). Effect of tartaric acid and dietary fibre from sun-dried raisins on colonic function and on bile acid and volatile fatty acid excretion in healthy adults. British Journal of Nutrition, 90(4), 803-807.