Ethylene glycol kills a 4 kg cat at roughly 6 mL, which is 1.2 US teaspoons, and the useful treatment window is 2 hours from the first lap. Three rules cover the whole emergency: do not make the cat vomit, do not wait for a symptom, and drive while someone else calls the clinic. The dose is small enough that a spill the size of a coin can carry it, and the taste is sweet enough that the cat drinks rather than avoids.
The dose is 1.5 mL per kg, and it is smaller than it sounds
The lethal dose of ethylene glycol concentrate for a cat is about 1.5 mL per kg, and kidney damage starts below that, from roughly 0.5 mL per kg. Run the math on the cat you own: a 2 kg cat is gone at 3 mL, a 3 kg cat at 4.5 mL, a 4 kg cat at 6 mL, a 5 kg cat at 7.5 mL, a 6 kg cat at 9 mL. A teaspoon holds 5 mL and a tablespoon holds 15 mL, so one tablespoon is 2.5 times the lethal dose for a 4 kg cat. A 50 percent mix halves the volume of pure glycol, so 12 mL of the diluted product still delivers 6 mL. A puddle 10 cm across and 2 mm deep holds about 15 mL, which is why a garage floor spill is not a small event.
Why the clock stops at 2 hours
Ethylene glycol is absorbed fast: blood levels peak between 1 and 2 hours after the cat drinks. The liver enzyme alcohol dehydrogenase then converts it to glycolaldehyde, then to glycolic acid, and finally to oxalate. The acid load is what drops blood pH and shuts the kidney down, and the oxalate binds calcium into crystals inside the kidney tubules. Metabolism is already under way by the 2 hour mark, so an antidote given at hour 3 has far less to block. That is the whole reason the window is measured in hours rather than days. Beyond 2 hours, treatment shifts to aggressive fluid support and, where available, dialysis, and the survival rate falls sharply.
0, 1, 2, 6 and 24 hours
| Hours after the lap | What you see | Urine output (mL/kg/h) | What to do |
|---|---|---|---|
| 0 hours | Nothing yet. Maybe drooling, or interest in the spill | 1 to 2 | Drive now, call on the way |
| 1 hour | Wobbly walk, vomiting, large pupils | 1 to 2 | Antidote window open |
| 2 hours | Vomiting, head pressing, fast breathing | 1 to 2 | Last useful moment to start the antidote |
| 6 hours | Looks better, drinks a lot, vomits less | 0.5 to 1 | Hospital, fluids; kidney injury forming |
| 24 hours | Seizures, little or no urine, cold, comatose | Under 0.2 | Dialysis or palliative care |
The trap sits at 2 to 6 hours, when the cat stops vomiting and walks straight again. Owners read that as recovery and go back to bed. It is the kidney working through the damage, and the cat is usually worse by hour 12 than it was at hour 2.
Never make the cat vomit
Three reasons, in order of importance. First, absorption is essentially complete by 30 to 60 minutes, so vomiting at hour 1 retrieves very little of a dose that was already 6 mL. Second, a cat that vomits and aspirates develops pneumonia, which turns a survivable poisoning into a second critical problem. Third, the 15 minutes spent hunting for salt, hydrogen peroxide or a syringe is 15 minutes off a 120 minute window, and the only intervention that changes the outcome is the antidote. Home remedies such as milk, cooking oil or alcohol make it worse: fat slows nothing and alcohol competes for the same enzyme without blocking it usefully. The clinic may pass a stomach tube and lavage within the first 30 to 60 minutes, but that is a decision for a vet with a catheter already in the leg.
What happens in the first hour at the clinic
A vet will run an ethylene glycol test that returns a result in about 10 to 15 minutes, plus a blood panel for pH, calcium, potassium and creatinine, and start intravenous fluids at 2 to 3 times maintenance rate to push the kidneys through. The specific antidote is fomepizole (4-MP), which blocks alcohol dehydrogenase before the glycol is converted; it is available only on prescription and only a veterinarian can give it. Ethanol is the older alternative and is used where fomepizole is not stocked. Ask for the test result as a number, and ask what the creatinine is, because those two numbers decide the next 24 hours far more than how the cat looks at the desk.
Six sources people forget in winter
Radiator coolant is the obvious one, at 30 to 50 percent glycol. Windshield washer fluid runs 20 to 40 percent in winter grades. Brake fluid, solar panel antifreeze for roof arrays, de-icing spray for locks, and the liquid inside a decorative snow globe all contain it. A snow globe holds 5 to 20 mL, which is a lethal dose for a 4 kg cat if it breaks on the floor. Toilet bowl cleaners and some aquarium products carry propylene glycol instead, which is far less toxic to cats, so read the label before you panic, and photograph the label while you drive. A spill on the driveway is its own job, covered in antifreeze spills, and the propylene versus ethylene question is one a toxic list answers in 30 seconds: toxicity checker.
A 10-minute sweep of the garage and porch
- Look for rainbow sheen or a sweet smell on the floor, driveway and doormat, and check under the car for a drip.
- Move every container into a closed cabinet above 150 cm, inside a second sealed bag or tray.
- Clean a spill with 2 paper towels, then cat litter, then 3 rinses of water, and bag all of it.
- Never hose a spill into the yard or the street, where it becomes a 10 m puddle the cat can reach.
- Keep the cat out of the garage entirely from the first frost to the last, and wipe the paws at the door.
Go even if the cat looks fine
There is no home test and no safe observation period. A cat that lapped from a spill 20 minutes ago and is walking normally has a normal exam and an abnormal blood glycol level, and the two do not match until hour 2. Call the clinic, say the words ethylene glycol and the cat's weight, and drive. If the cat is already vomiting, seizuring or breathing fast, say so on the phone so the team prepares before you arrive.
Terms mentioned in this article
Frequently asked
How much antifreeze does a cat have to drink to die?
About 1.5 mL per kg of concentrate, so a 4 kg cat is at risk from 6 mL, roughly 1.2 teaspoons. Kidney injury can begin from 0.5 mL per kg, which for the same cat is 2 mL, less than half a teaspoon. A 50 percent product doubles the volume needed to deliver that dose, and a small spill of 10 to 15 mL on a garage floor is already enough for two cats.
The cat seems fine two hours later. Can I wait until morning?
No. The 2 to 6 hour stretch is when vomiting stops and the cat walks normally again, and that apparent recovery is the kidney working through damage rather than healing. Blood glycol peaks at 1 to 2 hours and crystals start forming in the tubules from about hour 3. By hour 12 the cat is usually far worse, so a normal-looking cat at hour 2 is still an emergency that needs a test and fluids.
Should I make the cat vomit before driving?
No. Absorption is essentially complete within 30 to 60 minutes, so vomiting mostly returns food and bile, and it risks aspiration pneumonia in a cat that is already unsteady. It also costs 15 to 30 minutes out of a 120 minute window, and the antidote is what changes the outcome. Do not give milk, oil, salt or alcohol either. Drive, and let the vet decide about lavage in the first hour.