Washer fluid sold for -20 C and -35 C winters is mostly methanol; pink or green all-season fluid is mostly ethylene glycol, and the two poisons hit different organs on different clocks. Methanol becomes formic acid and attacks the optic nerve, ethylene glycol becomes oxalate crystals that plug the renal tubules. Both are absorbed inside 30 minutes, so call a veterinarian first and never make the cat vomit.
Two Recipes, Two Targets
Read the jug before you read the cat. A -20 C fluid is typically 20 to 35 percent methanol with blue dye; -35 C and -40 C grades climb to 40 to 50 percent. Pink or green all-season fluid usually carries 10 to 30 percent ethylene glycol, sometimes with 1 to 5 percent methanol on top. Summer bug-wash sits under 5 percent solvent, though its surfactants still cause vomiting.
Concentration beats puddle size. A 3.78 L jug at 40 percent holds about 1.5 L of pure methanol, and each milliliter of fluid carries 0.4 ml. A 4 kg cat lapping 5 ml takes 2 ml of methanol; the same 5 ml of a 30 percent glycol fluid gives 1.5 ml of ethylene glycol, a quarter of the 6 ml that kills an average 4 kg cat.
The 30-Minute Line
Alcohols cross the stomach wall within minutes, and blood levels peak at 30 to 60 minutes on an empty stomach, 60 to 90 after a meal. Triage scripts ask for the clock time of the lick, not the volume. Under 30 minutes most of the dose may still be in the gut; past 60 the liver is already converting it.
A cat steady at 20 minutes can be ataxic at 45 and vomiting at 90. Note the time, photograph the label, and keep the cat in a towel-lined carrier at 20 to 24 C; a cat that drops to 36 C is harder to stabilize.
Target One: The Optic Nerve
The poison is formic acid, not methanol. Alcohol dehydrogenase converts methanol to formaldehyde then formic acid, which blocks cytochrome oxidase, so retinal and optic nerve cells cannot use oxygen even when blood flow is normal. The same metabolite drives acidosis, with pH under 7.2 and bicarbonate under 12 mmol/L in severe cases.
Eye signs arrive at 6 to 24 hours: a pupil that stays dilated, a lost menace response, no tracking of a hand in dim light. Methanol blindness is often permanent and can be complete within 24 to 48 hours. A cat bumping into furniture at 6 hours needs a clinic, not a night of observation.
Target Two: The Renal Tubule
Ethylene glycol is oxidized to glycolaldehyde, glycolate, then oxalate. Oxalate binds calcium into monohydrate crystals that lodge in the proximal tubules, and the tubules die while the cat still looks drunk rather than sick. Crystals appear in urine from 3 to 6 hours, so a urine sample at hour 6 beats a chemistry panel at hour 2.
Kidney values lag. Creatinine often doubles by 24 to 36 hours, urine output falls under 1 ml/kg per hour by 24 hours, and anuria follows at 36 to 72. An anion gap above 20 mmol/L with an osmol gap above 10 mOsm/kg in the first 6 hours is the pattern clinics look for. Blocked tubules do not reopen.
Hour by Hour: 0, 1, 2, 6, 24
| Hour | Methanol fluid | Glycol fluid | Action |
|---|---|---|---|
| 0 to 30 min | Drooling, gait normal | Drooling, early head pressing | Call vet, cap the jug |
| 1 h | Wobbling, pupils wide, 38 to 42 breaths/min | Vomiting 2 to 5 times, drunk gait | Drive, no vomiting |
| 2 h | Head tilt, pH below 7.3 | Severe ataxia, heart rate above 200 | Blood gas, osmol gap, urine |
| 6 h | Weak menace reflex, pupils fixed at 6 to 8 mm | Oxalate crystals, creatinine 1.5 times baseline | Antidote, fluids, dialysis call |
| 24 h | Blind, bicarbonate near 12 mmol/L | Urine under 1 ml/kg/h, creatinine 2 to 3 times baseline | ICU and dialysis, guarded |
The table is a map, not a schedule. A cat that laps 10 ml rather than 5 ml can jump two rows.
Why Nobody Should Make the Cat Vomit
Induced vomiting is the most common home mistake. Absorption takes 15 to 30 minutes for a small alcohol dose, so most of it is in the blood by the time the cat retches. Aspiration is likely: 1 to 2 ml of foaming surfactant fluid in the airway causes chemical pneumonia that can kill days later. Vapor is inhaled as the fluid comes up, and the attempt costs 20 to 40 minutes of driving time.
Charcoal is no substitute. It binds alcohols and glycols poorly, well under 10 percent, and does nothing once the dose has passed the stomach. Milk, oil, and raw egg are wasted minutes; fat neutralizes neither poison.
Antidotes Are a Prescription Decision
Two antidotes exist and both need a veterinarian. Fomepizole blocks alcohol dehydrogenase and is the first choice in most clinics; ethanol is the older alternative where fomepizole is unavailable. Neither is a household item, both are given under veterinary prescription, and the amount depends on weight, blood pH, and time since exposure, so no figure belongs in a home kit. Support runs alongside: IV fluids, bicarbonate, antiemetics, and hemodialysis, best started within 6 to 8 hours. Ask whether the clinic stocks fomepizole and can run a glycol test in 15 to 30 minutes.
What to Bring, and What the Vet Will Ask
Bring the jug or a photo of the label with concentration and temperature rating legible, plus the time, the weight, and how much fluid is missing. First-hour tests usually include blood gas, anion and osmol gaps, BUN, creatinine, and urine sediment. A normal creatinine at hour 2 does not clear a 4 kg cat; it can stay normal for 12 to 24 hours while tubules fail. The toxic dose calculator puts a figure on the exposure before you call.
Survivors often run creatinine above 2.0 mg/dL and urinate 40 to 60 ml/kg per day. Recheck at 7 days, 30 days, and 3 months, and follow the long-term subcutaneous fluid routine if home fluids are prescribed.
Storage Rules That Hold Up
Keep the jug above 150 cm in a closed cabinet and never decant it into a drink bottle. Wipe the filler neck and windshield tray after each top-up, because a cap holds 15 to 20 ml and a cat will lick it dry. Rinse spills with 2 L of water; a 5 ml puddle on tile is a full dose for a small cat.
First 30 Minutes, in Order
- Move the cat off the puddle and close the jug.
- Call a veterinarian or poison hotline with methanol or glycol, the clock time, and the weight.
- Photograph the label and note the -20 C or -35 C rating.
- Carry the cat in a closed carrier; do not induce vomiting.
- Call ahead so the antidote is ready, and read fluid therapy basics if a bolus starts.
Terms mentioned in this article
Frequently asked
How much windshield fluid does it take to harm a cat?
There is no safe threshold, but the arithmetic is simple. A 40 percent methanol fluid carries 0.4 ml of pure methanol per milliliter, so a 5 ml lap gives a 4 kg cat about 2 ml of methanol. A 30 percent glycol fluid at 5 ml delivers 1.5 ml of ethylene glycol, a quarter of the 6 ml dose that kills an average 4 kg cat. Treat any deliberate lap as an emergency.
Can I make my cat vomit after it drinks washer fluid?
No. Alcohols and glycols are absorbed within 15 to 30 minutes, so vomiting rarely removes much, and 1 to 2 ml of foaming surfactant fluid in the airway can cause chemical pneumonia. Charcoal binds these compounds poorly, under 10 percent in most references, and home remedies only cost the 20 to 40 minutes of driving time the cat does not have.
Will a cat blinded by methanol see again?
Sometimes, but the damage is often permanent. Formic acid blocks energy use in retinal and optic nerve cells, and signs appear between 6 and 24 hours. Cats that reach a clinic within the first 2 hours and receive an antidote plus acid-base support have the best chance of keeping vision. A cat with no menace response at 24 hours needs an ophthalmology referral.