Antifreeze toxicity is, unfortunately, one of the most common poisonings of dogs, cats, and many other animals who like the taste of it, including birds.  It is often left in uncovered containers or puddles from drained radiators, and any pet on the loose may soon find it.  It doesn’t take much for an animal to be poisoned—about 4.5 ounces for a 20-lb dog, or one tablespoon for the average cat.

The toxic substance in antifreeze is called ethylene glycol.  This chemical is very toxic, and has one of the highest fatality rates of all poisons.  As with any toxin, prevention is the best cure: keeping your pets from wandering and getting exposed.

Wht to Expect

There are three stages of poisoning, and the first two may or may not be noticeable, even to veterinarians, if brought into a clinic right away.

  • Stage 1: 30 minutes to 12 hours  Initially, depending on how much was ingested, you might see vomiting, depression, increased thirst and/or urination, trouble walking, and even seizures.  If enough antifreeze was ingested, coma and death could occur within this time.
  • Stage 2: 12 to 34 hours after ingestion  Heart rate and breathing increases.  Other signs may abate temporarily, giving a false sense of recovery.
  • Stage 3: 24 to 72 hours after ingestion for dogs and 12-24 hours in cats  The kidneys begin to fail, diarrhea may occur, and you may see more vomiting and severe depression.  Coma and death may follow within a day.

If you suspect your pet has ingested antifreeze, bring it to a veterinarian immediately.  If you wait until symptoms occur, it may be too late.

There is a blood test available that can detect ethylene glycol, but it is only good up to 6 hours after ingestion.  If it is determined that the animal has been poisoned, treatment can begin immediately.  A wide range of other clinical tests can be run to monitor the patient’s progress during recovery.


If the antifreeze was recently ingested, vomiting may be induced to remove as much from the stomach as possible.  Activated charcoal may be given to absorb more.  IV fluids are given to correct dehydration and numerous drugs may help to neutralize the toxin.

Since the kidneys may be damaged, long-term care may be necessary.  If the damage is permanent, the animal may never fully recover.  Consult your veterinarian if you have further questions.