Ethylene glycol (antifreeze) in Pets

A teaspoon of antifreeze can kill a cat. Convert millilitres to mg/kg, compare with Merck's lethal doses (1.4 mL/kg cats, 4.4–6.6 mL/kg dogs) and see why the first hours matter.

What It Is

Ethylene glycol is the main ingredient in many car antifreezes and coolants, and it tastes sweet. The body converts it into glycolic acid and oxalic acid, which cause severe acid build-up and form calcium oxalate crystals that destroy the kidneys.

Where Pets Come Across It

Drips from car radiators on driveways, coolant left in open containers in garages, some windscreen de-icers and brake fluids, and antifreeze poured into toilets of holiday homes. Some products now include a bittering agent, but that does not make them safe.

Which Animals Are Affected

Cats are the most sensitive, followed by dogs. Many other animals, including birds and livestock, can be poisoned.

Published Toxic Dose

The Merck Veterinary Manual lists the minimum lethal dose of undiluted ethylene glycol as 1.4 mL/kg in cats and 4.4–6.6 mL/kg in dogs. Ethylene glycol weighs about 1.11 g per mL, so 1.4 mL/kg is roughly 1,550 mg/kg. Coolant is often sold as a 50% mix, which halves the dose per mL swallowed. A teaspoon (5 mL) of concentrate can kill a cat.

Signs and How Soon They Appear

From 30 minutes to 12 hours the animal appears drunk: wobbly, vomiting, thirsty and urinating a lot. It may then seem to recover around 12 hours. Kidney failure follows, from about 12 to 24 hours in cats and 36 to 72 hours in dogs: no appetite, vomiting, very little urine, seizures and coma.

What to Do Right Now

Go to a vet immediately if you even suspect antifreeze exposure. The antidote only works if it is given early, within hours of drinking, and cats have the shortest window. Bring the container. Do not wait for signs and do not induce vomiting at home.

Frequently Asked Questions

Sources and References

• Merck Veterinary Manual: Ethylene Glycol Toxicosis in Animals
• ASPCA Animal Poison Control Center

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