CONDITION
Ethylene Glycol Toxicity
Ethylene glycol toxicity occurs when a dog or cat ingests antifreeze or certain other products containing this sweet-tasting chemical. Once absorbed, ethylene glycol is metabolised in the liver into compounds that can cause severe damage to the kidneys, among other effects. The window between ingestion and the development of serious metabolic changes tends to be short, often measured in hours rather than days. Owners most commonly arrive at this topic after a known or suspected ingestion—perhaps antifreeze has been spilled in the garage, or a pet has been found near a puddle with a sweet smell. Early signs can include behaviour that appears similar to intoxication: unsteadiness, increased thirst, vomiting. Later signs may reflect worsening kidney function, though the progression and severity vary with the amount ingested and how quickly intervention occurs. This page explores the signs that may be observed, the metabolic processes that lead to kidney injury, how ethylene glycol exposure is investigated in practice, and the approaches used to interrupt the toxic pathway and support kidney function. The content is intended to help you understand what may be happening and what shape the conversations and decisions ahead might take.
Why this matters now
Ethylene glycol toxicity can occur at any age and affects both dogs and cats, though cats tend to require a smaller volume to produce severe effects. Exposure often happens in colder months when antifreeze is in use, or in settings where windscreen wash, brake fluid, or certain industrial products are accessible. The condition is not linked to breed, sex, or life stage—what matters is opportunity for ingestion and the appeal of the sweet taste.
The sequence of metabolic changes typically unfolds in stages over the first 12 to 72 hours, though the timing and severity vary with the amount ingested and the individual animal's metabolism. Early effects may appear within 30 minutes to a few hours and can include signs that resemble mild intoxication. As ethylene glycol is converted into toxic metabolites, the clinical picture often shifts towards metabolic disturbance and, in many cases, progressive kidney injury. The speed of progression means that the shape of the condition at 6 hours may differ markedly from what is observed at 24 or 48 hours.
Signals & patterns
Early signals
Unsteadiness or wobbly gait
Within the first few hours, a dog or cat may appear uncoordinated, as though slightly drunk—stumbling, swaying, or having difficulty walking in a straight line. This reflects the initial effects of ethylene glycol on the nervous system before metabolism into more harmful compounds has fully occurred.
Increased thirst and urination
Many animals begin drinking more water than usual and may urinate more frequently or in larger volumes shortly after ingestion. This can reflect the body's attempt to process and excrete the foreign substance, as well as early changes in how the kidneys handle fluid.
Vomiting
Vomiting may occur within the first few hours and can be a non-specific response to gastrointestinal irritation or the systemic effects of the toxin. The vomit itself does not typically have a distinctive appearance.
Lethargy or dullness
Some animals become quieter or less responsive than usual, seeming subdued or reluctant to interact. This may overlap with the period of apparent intoxication and can persist as metabolic changes develop.
Increased breathing rate
Faster or more effortful breathing can appear as the body begins to respond to metabolic acidosis—a shift in blood chemistry that the lungs attempt to correct by expelling more carbon dioxide.
Later signals
Reduced or absent urine production
After the initial period of increased urination, some animals may produce very little urine or none at all, reflecting worsening kidney function. This change often becomes apparent 24 to 72 hours after ingestion.
Weakness or collapse
As kidney injury progresses and metabolic disturbances accumulate, an animal may become profoundly weak, reluctant to stand, or unable to support its own weight. This reflects the systemic impact of failing kidney function and metabolic imbalance.
Seizures or twitching
In some cases, particularly in cats, neurological signs such as muscle twitching or seizures may develop later in the course. These can be linked to severe metabolic derangement, including low calcium levels and accumulation of toxic metabolites.
Click to read about the biological mechanisms
How this is usually investigated
The investigation typically begins with a careful history, focusing on recent opportunity for access to antifreeze, windscreen wash, or similar products, alongside the timing and pattern of signs observed at home. Physical examination may reveal findings consistent with the stage of toxicity—unsteadiness and increased thirst in the early hours, or signs of metabolic disturbance and deteriorating kidney function later. Laboratory tests are then used to detect ethylene glycol itself, to assess the degree of metabolic acidosis, and to evaluate kidney function, though the availability and timing of specific tests can shape the picture that emerges.
Blood biochemistry
Ethylene glycol test
Urinalysis
Blood gas analysis
Physical examination
Options & trade-offs
Management of ethylene glycol toxicity tends to involve a combination of approaches, shaped by the time since ingestion, the stage of metabolic disturbance, and what is available in the setting where care is being provided. Early intervention focuses on interrupting the conversion of ethylene glycol into toxic metabolites, while later care often centres on supporting kidney function and managing the consequences of acidosis. The combination and intensity of approaches vary from case to case, and what is workable for one household or one animal may differ for another.
Alcohol dehydrogenase inhibition
Substances such as ethanol or fomepizole compete with ethylene glycol for the enzyme alcohol dehydrogenase, slowing the formation of toxic metabolites. This approach is most effective when started soon after ingestion, ideally within the first few hours. Fomepizole is typically given by intravenous infusion, while ethanol may be administered intravenously or, less commonly, by other routes.
Trade-offs: The effectiveness of this approach diminishes as time passes and more ethylene glycol is metabolised. Fomepizole availability varies, and ethanol carries its own risks of intoxication and requires careful monitoring. Neither eliminates ethylene glycol that has already been converted, so kidney injury may still progress if metabolites have accumulated before treatment begins.
Intravenous fluid therapy
Administration of fluids by vein supports kidney function by maintaining blood flow to the kidneys and promoting the excretion of toxins through urine. Fluids can also help to correct dehydration and support the body's attempts to buffer metabolic acidosis. The volume, rate, and composition of fluids are adjusted over time based on hydration status, urine output, and laboratory findings.
Trade-offs: Fluid therapy is supportive rather than curative—it does not reverse damage that has already occurred, nor does it prevent the formation of toxic metabolites. In cases where kidney function is severely compromised, the ability to produce urine may be limited, and close monitoring is needed to avoid fluid overload.
Correction of metabolic acidosis
Bicarbonate may be given intravenously to help restore blood pH towards normal range when acidosis is severe. The dose and frequency are guided by repeated blood gas measurements, and the goal is to reduce the metabolic burden while the underlying cause is addressed.
Trade-offs: Bicarbonate therapy addresses the consequence of the toxic metabolites rather than the metabolites themselves, and its effect is temporary if the production of acid continues. Overcorrection carries its own risks, and the response varies between individuals.
Haemodialysis
In settings where it is available, haemodialysis can directly remove ethylene glycol and its metabolites from the bloodstream, as well as correct severe acidosis and support kidney function when the kidneys are unable to do so. The process involves circulating the blood through an external filter and is typically performed over several hours.
Trade-offs: Haemodialysis requires specialised equipment and expertise, and access is limited to referral centres. The procedure itself carries risks, particularly in unstable patients, and the outcome depends heavily on the degree of kidney injury present before dialysis begins. It is most often considered when other approaches have not halted the progression of toxicity or when kidney function is severely compromised.
Gastric decontamination
If ingestion has occurred within the previous hour or two, inducing vomiting or performing gastric lavage may reduce the amount of ethylene glycol absorbed into the bloodstream. This is a time-sensitive intervention and is typically only considered when the animal is still alert and able to protect its airway.
Trade-offs: Once ethylene glycol has been absorbed—often within 30 to 60 minutes—gastric decontamination offers little benefit and may carry risks, particularly if the animal is already showing neurological signs. The decision to attempt this step depends on a narrow window of opportunity and the individual animal's condition.
Common misconceptions
"If a pet seems to recover after a few hours, the danger has passed."
The early signs of ethylene glycol toxicity—unsteadiness, increased thirst, vomiting—may appear to resolve as the initial effects on the nervous system subside, even while toxic metabolites continue to accumulate and kidney injury progresses. This temporary improvement can occur in the period between the early neurological phase and the later onset of kidney failure, and it does not indicate that the toxic process has stopped.
"Only large amounts of antifreeze are dangerous."
The volume required to cause toxicity is smaller than many owners expect, particularly in cats. A few tablespoons can be sufficient to produce severe effects in a cat, and dogs are affected by volumes that might seem modest given their size. The sweet taste makes even small spills or puddles appealing, and ingestion of what appears to be a minor quantity can still lead to serious metabolic consequences.
"A negative test for ethylene glycol means the pet is safe."
Tests that detect ethylene glycol in blood or urine are most reliable in the early hours after ingestion. If the test is performed later—after much of the ethylene glycol has already been metabolised—it may return a negative result even though toxic metabolites are present and kidney injury is underway. The timing of the test matters as much as the result itself, and clinical suspicion may remain even when a late test is negative.
Related conditions
Acute Kidney Injury
Ethylene glycol toxicity is one of the causes that can lead to acute kidney injury, as the metabolic breakdown products of ethylene glycol damage the kidneys' filtering structures. The signs and laboratory changes seen in ethylene glycol exposure often overlap with those of acute kidney injury from other causes.
Grape and Raisin Toxicity in Dogs
Grape and raisin toxicity shares with ethylene glycol toxicity the pattern of ingestion-related sudden kidney injury, though the substances and metabolic pathways differ. Both tend to produce signs within hours and prompt similar conversations about the timing of intervention and support for kidney function.
Lily Toxicity in Cats
Lily toxicity in cats parallels ethylene glycol toxicity in that both involve rapid kidney damage following ingestion of a substance that may initially seem innocuous. The short window between exposure and irreversible injury, and the urgency of early metabolic support, are features common to both.
Ibuprofen Toxicity
Ibuprofen toxicity can produce kidney injury in addition to gastrointestinal and neurological effects, and may be considered in a similar context to ethylene glycol when investigating known or suspected ingestion. The metabolic insult to the kidneys differs in mechanism, but the clinical picture and investigation pathways often overlap.
Acute Hepatic Failure
While ethylene glycol primarily targets the kidneys, the liver is the organ responsible for metabolising ethylene glycol into its toxic breakdown products. In severe cases, liver injury may occur alongside kidney damage, though the kidney effects tend to dominate the clinical picture.
Ethylene glycol toxicity sits within the broader context of metabolic health, where the body's chemical balance can shift rapidly in response to ingested substances, organ injury, or systemic illness. Understanding how the kidneys respond to different challenges, and what shapes their capacity to recover, may be useful as you think through the patterns you have observed and the conversations that lie ahead. Other topics within metabolic health explore related mechanisms and the factors that influence prognosis in conditions affecting kidney function and acid-base balance.