Antifreeze Poisoning in Dogs: What Happens in the Dog’s Body with Antifreeze Poisoning?

Most dog owners are aware that antifreeze containing ethylene glycol (EG) is dangerous stuff.

But, do you know exactly how antifreeze wreaks havoc in a dog’s body?

I didn’t think so (I had to look up a few of the finer points too). Let’s review how the dog’s body absorbs, metabolizes, and excretes ethylene glycol. The information is essential to understanding why antifreeze poisoning has to be treated so quickly.

Antifreeze Poisoning in Dogs: What Happens in the Dog’s Body with Antifreeze Poisoning?

Antifreeze toxicity

It does not take much antifreeze to make dogs REALLY sick.

The minimum lethal dose of ethylene glycol is 2-3 ml/lb. In other words, less than 2 fluid ounces can kill a 20-pound dog.

So I’m going to invent a 20-pound dog.

His name is Rascal, and he just found a puddle of sweet-smelling liquid underneath his neighbor’s leaky old car (someone left his backyard gate open, but he stays close to home). He tastes it and thinks, “Not bad” and proceeds to lap up the rest of the antifreeze… you guessed it, about two ounces worth.

Fast absorption

Before his owners even realize he’s out of the yard, the ethylene glycol is making its way into Rascal’s bloodstream.

He wanders home, is let inside, and within just a few hours starts acting a little funny. He’s very thirsty but dull and depressed, and when he tries to walk he looks like he’s drunk… stumbling and swaying from side to side. This occurs because EG can easily cross into the cerebrospinal fluid that bathes the brain and once there, has an adverse effect on neurological function.

Two scenarios

Now our tale can go in one of two ways:

  1. Rascal’s owners think, “Uh oh, he was just out of the yard and now he’s not right. Let’s get him to the vet’s ASAP” or
  2. “Huh, isn’t that funny. I bet he’ll feel better in the morning.”

Scenario #1

Let’s make #1 our best-case scenario.

Rascal’s owners bring him in, mention that he’s been roaming the neighborhood, and based on this history and Racal’s clinical signs the vet thinks of the possibility of antifreeze poisoning. The bench-top test comes back positive, and Rascal is immediately given activated charcoal, put on intravenous fluid therapy, and treated with either a diluted ethanol solution or fomepizole, either of which will compete with one of the enzymes needed to convert EG into its toxic metabolites as long as it is given within eight hours of ingestion. After several days of hospitalization, treatment, and close monitoring, Rascal is sent home and recovers uneventfully.

Scenario #2

Now on to scenario 2:

As the hours pass (12-24) without diagnosis or treatment, Rascal’s liver starts to metabolize the ethylene glycol, first into glycoaldehyde, then glycolic acid, and finally glyoxylic acid, which makes the body more acidic than normal.

Rather than getting better, he now is breathing heavily, is coughing a little, and his heart is racing.

Approximately 24 hours after exposure, Rascal is starting to break down the glyoxylic acid that has formed, creating oxalic acid that combines with calcium to form calcium oxalate crystals (and low blood calcium levels). The calcium oxalate crystals travel through his bloodstream and become lodged in and severely damage his kidneys. Rascal wants to drink a lot of water but is urinating out all he takes in. As more and more damage accrues (24-72hrs), Rascal has so little kidney function left that substances like blood urea nitrogen and creatinine accumulate in his bloodstream, he no longer produces much if any urine, his mouth becomes ulcerated, he starts having seizures, and he will die without dialysis and a kidney transplant.

Don’t let your dogs be victims of scenario two.

Bring them to the veterinarian immediately if you ever have reason to suspect they have ingested antifreeze.

Related articles:
Symptoms to Watch for in Your Dog: Green Vomit

Further reading:
Ethylene Glycol Poisoning

  1. Thanks for this important illustration about the need to take action if you think your dog has ingested antifreeze. I wonder if there is a way to make antifreeze taste unpleasant to dogs and still work.

  2. This sounds nasty. I know people rant on about cats getting at antifreeze but I had no idea it could have such a nasty effect on dogs. It must be a tricky call but if you know your dog it should help you make the right decision. I hope a lot of people read your post especially as its winter in the northern hemisphere!

  3. FiveSibesMom

    Always a scary thought…we keep ours in the garage way up high where the dogs cannot get to it. But it is so scary because supposedly it is “sweet tasting”… and if you do not see them get into something, it can be life threatening. As always, great info.

  4. Wow! Inventing Rascal truly made this frightening topic much more accessible. I have definitely struggled with those “Huh, you’re acting funny” moments with our dogs. I liked the reminder about context for scenario #1. Thinking about how Rascal was just outside unsupervised, and now is acting odd, is such a game changer in the struggle to head to the vet. Or at least call your vet to describe what you’re seeing. Our vet’s receptionist asks great questions about context that help her figure out how to triage phone calls.

  5. That’s a frightening scenario. I didn’t realize that dogs were attracted to antifreeze too. I’ve heard that some? All? Brands have added something to make it gross to animals? Definitely something to be aware of

    • Yes, some brands add some bittering agent. And there seem to be some safe products out there but unfortunately those don’t work when it gets really cold.

  6. Yikes, this is so tricky. I admit, I don’t rush off to the vet when my pup acts a little off. I bet it is hard to figure out if pet parents are unaware that the dog has licked the antifreeze. Thank you for the reminder to keep us watching our pups when they go outside or are near the driveway where some antifreeze might be lurking. From: Ava Jaine, Dachshund Station.

    • Yes, figuring out what might be going on can be sometimes tricky for sure. It is always better to be safe than sorry, though.

    • That is absolutely an advantage. We can get temperatures down to -30 degrees Celsius so, unfortunately, gotta have antifreeze.

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