For an average-sized adult, roughly 100 milliliters of pure ethylene glycol, about three to four fluid ounces, is estimated to be lethal without treatment. That works out to around 1.4 to 1.6 milliliters per kilogram of body weight.1PubMed. Ethylene glycol: an estimate of tolerable levels of exposure based on a review of animal and human data But that number deserves a lot of context, because lethality depends heavily on how quickly the person receives medical treatment, whether they have consumed alcohol around the same time, and what concentration of ethylene glycol they actually drank.
Where the Lethal Dose Estimate Comes From
The often-cited figure of about 100 mL for a 70-kilogram adult (roughly 154 pounds) is drawn from case reports of poisoning, not controlled experiments. Researchers cannot ethically dose humans with a known poison, so lethal-dose estimates come from reviewing fatal and near-fatal cases and working backward from blood levels and reported volumes consumed. That makes the number an approximation, not a hard threshold. Some people have survived far larger ingestions with aggressive treatment, and some have died after swallowing less.1PubMed. Ethylene glycol: an estimate of tolerable levels of exposure based on a review of animal and human data
Ethylene glycol itself is only modestly toxic. It is what happens inside the body after absorption that makes it so dangerous. Once swallowed, ethylene glycol is rapidly absorbed through the gastrointestinal tract and distributed through body water. Less than a fifth of the absorbed compound is excreted unchanged in urine; the rest is broken down in the liver into a cascade of increasingly harmful byproducts. It is those metabolites, not the parent compound, that cause organ failure and death.
How the Body Turns Ethylene Glycol Into Poison
Ethylene glycol on its own acts mostly as a central nervous system depressant, producing effects similar to alcohol intoxication. The real damage begins when the liver enzyme alcohol dehydrogenase starts breaking it down. The first product is glycolaldehyde, which is quickly converted to glycolic acid (also called glycolate). Glycolic acid is the main driver of the dangerous metabolic acidosis that characterizes serious ethylene glycol poisoning, essentially flooding the blood with acid and overwhelming the body’s buffering systems.2PubMed Central. Severe ethylene glycol intoxication with marked lactate and osmolar gaps leading to acute kidney injury: a case report
Glycolic acid is then further metabolized to glyoxylic acid and eventually to oxalic acid. Oxalic acid binds to calcium in the blood and forms calcium oxalate crystals. Those crystals deposit in the kidneys, particularly in the cells lining the small tubules that filter urine, and cause acute kidney injury. Research has shown it is the physical crystals themselves, not free-floating oxalate, that do the most cellular damage. The crystals are taken up by kidney tubule cells and destroy them from the inside.3PubMed. The cytotoxicity of oxalate, metabolite of ethylene glycol, is due to calcium oxalate monohydrate formation Acidic conditions make the crystal damage worse, which is a vicious cycle: the metabolic acidosis caused by glycolate makes the kidney injury from oxalate crystals more severe.4PubMed. Renal toxicity of ethylene glycol results from internalization of calcium oxalate crystals by proximal tubule cells
One clinically important finding is that blood levels of ethylene glycol itself correlate poorly with how sick someone actually is. In a study examining this relationship, glycolic acid levels tracked closely with the severity of acidosis, while ethylene glycol concentrations did not.5PubMed. Ethylene glycol toxicity: the role of serum glycolic acid in hemodialysis That means a patient who drank ethylene glycol hours ago might have very little of the parent compound left in their blood but be critically ill from the metabolites it produced. This is one of the reasons the 100 mL lethal dose figure is so slippery: timing matters enormously.
What Happens in the Hours After Ingestion
Ethylene glycol poisoning typically unfolds in a rough three-stage pattern, though not every patient progresses neatly through each stage. In the first few hours, the dominant effect is something that looks like severe alcohol intoxication: confusion, slurred speech, nausea, and vomiting. Because ethylene glycol has a slightly sweet taste and no strong odor, people around the victim may not realize anything unusual has been consumed. Blood tests at this point may show a high osmolar gap (meaning there is an unexplained solute in the blood), but the more familiar signs of poisoning may not have appeared yet.
Over the next twelve to twenty-four hours, the metabolic phase takes hold. Glycolic acid accumulates and produces a severe, high-anion-gap metabolic acidosis. Heart rate and breathing rate climb as the body tries to compensate for the acid load. Calcium levels can drop because calcium is being bound up into oxalate crystals, which can cause muscle twitching and cardiac rhythm problems. If untreated, this stage can be fatal.
The third stage, typically appearing twenty-four to seventy-two hours after ingestion, centers on the kidneys. Calcium oxalate crystals clog the renal tubules, urine output drops, and acute kidney injury sets in. Even patients who survive the metabolic acidosis can end up on dialysis for days or weeks while their kidneys recover, if they recover at all.6PubMed Central. Ethylene Glycol Poisoning With Oxalate Nephropathy and Acute Kidney Injury: A Case Report and Review of the Literature
Why Concentration and Product Type Matter
The 100 mL figure assumes pure or near-pure ethylene glycol, which is what you find in most conventional automotive antifreeze (typically 95% or higher concentration). But ethylene glycol shows up in a surprising range of household and industrial products at varying concentrations: hydraulic brake fluid, some de-icing solutions, certain paints, and even some older formulations of ink or shoe polish. The concentration matters because a swallow of a product that is 10% ethylene glycol delivers far less poison than the same swallow of undiluted antifreeze.
Clinical guidelines reflect this distinction. For concentrated products, adults who swallow even a small mouthful (in the range of 10 to 30 mL) are generally advised to go to the emergency room immediately. For dilute solutions below about 20% concentration, the potentially toxic volume is larger and can be estimated based on the person’s weight and the product’s actual ethylene glycol content.7PubMed. Ethylene glycol exposure: an evidence-based consensus guideline for out-of-hospital management Children are a special concern because their lower body weight means a smaller absolute volume is dangerous. Even a taste or lick of a concentrated ethylene glycol product in a child warrants medical evaluation if the exact amount is unknown.
How Alcohol Changes the Equation
If someone who has been drinking alcohol also ingests ethylene glycol, the clinical picture changes in an important way. Ethanol (drinking alcohol) and ethylene glycol are both broken down by the same enzyme: alcohol dehydrogenase. Ethanol has a higher affinity for that enzyme, meaning the liver preferentially processes ethanol first and lets ethylene glycol wait in line.8PubMed Central. Oral Ethanol Treatment for Ethylene Glycol Intoxication While the ethylene glycol is waiting, it stays in its relatively less toxic parent form and is gradually excreted by the kidneys.
This is actually the basis of one of the two medical treatments for ethylene glycol poisoning. In hospitals that do not have the preferred antidote on hand, intravenous ethanol is given to compete for alcohol dehydrogenase and slow the production of toxic metabolites. The half-life of ethylene glycol in the body, normally about three to eight hours, increases significantly when ethanol is co-ingested. This buys time but does not eliminate the compound, so further treatment is still needed.
This enzyme-competition effect also explains a real-world pattern: people who consume ethylene glycol while already drunk may appear less acutely ill at first than someone who drinks the same amount on an empty, sober stomach. That delay can be deceptive. Once the ethanol is metabolized and the liver turns its attention to ethylene glycol, the toxic metabolites come rushing in.
Treatment With Fomepizole and Hemodialysis
The preferred antidote today is fomepizole (brand name Antizol), a drug that directly blocks alcohol dehydrogenase far more predictably than ethanol does. A landmark trial showed that when fomepizole was given early in the course of ethylene glycol poisoning, it prevented kidney injury by stopping the formation of toxic metabolites before they could accumulate.9PubMed. Fomepizole for the Treatment of Ethylene Glycol Poisoning Fomepizole is easier for medical teams to manage than ethanol infusions, which require constant blood-alcohol monitoring and can cause their own sedation problems in an already-intoxicated patient.10PubMed. Ethylene glycol or methanol intoxication: which antidote should be used, fomepizole or ethanol?
For patients who present late or who have already developed significant acidosis or kidney failure, blocking the enzyme is not enough because the toxic metabolites are already in the blood. Hemodialysis is used to physically remove both ethylene glycol and glycolic acid from the circulation. A systematic review by the EXTRIP workgroup recommended hemodialysis when ethylene glycol blood concentrations exceed a certain threshold, when there is a large osmolar gap, or when severe clinical signs like coma, seizures, or kidney injury are present.11PubMed Central. Extracorporeal treatment for ethylene glycol poisoning: systematic review and recommendations from the EXTRIP workgroup During high-efficiency hemodialysis, the half-life of ethylene glycol drops to under three hours, allowing hospitals to clear the poison relatively quickly.12PubMed. Prediction and validation of the duration of hemodialysis sessions for the treatment of acute ethylene glycol poisoning
The bottom-line clinical reality is that ethylene glycol poisoning is highly survivable if caught and treated early, and often fatal if treatment is delayed. The lethal dose estimate of about 100 mL assumes no treatment. With prompt fomepizole and, if needed, hemodialysis, patients have survived ingestions well above that number.
Long-Term Consequences for Survivors
Surviving the acute poisoning does not always mean a clean recovery. The kidneys bear the brunt of the damage, and patients who developed acute kidney injury during the poisoning remain at elevated risk for chronic kidney disease even after their numbers improve. Factors that predict worse long-term outcomes include the severity of the initial acidosis, elevated potassium levels, and any neurological symptoms during the acute illness.13PubMed Central. Severe Ethylene Glycol Toxicity: Multidisciplinary Management and Long-Term Renal Implications
There is also a delayed neurological syndrome that can appear five to twenty days after the poisoning. The most common manifestation is cranial nerve damage, particularly affecting the facial nerve, which can cause weakness or paralysis on one or both sides of the face. Some patients have developed Parkinsonism or brain swelling.14PubMed. Delayed neurological sequelae from ethylene glycol, diethylene glycol and methanol poisonings These neurological effects can occur even in patients who seemed to be recovering well from the metabolic and renal phases of the poisoning, which makes follow-up monitoring important.
How Forensic Investigators Confirm Fatal Poisoning
In forensic settings, confirming that someone died from ethylene glycol is not as straightforward as measuring how much is in their blood. Because the body continues to metabolize ethylene glycol after ingestion, a person who survives long enough for the liver to process most of the compound may have very low blood ethylene glycol at the time of death, even though they died from its effects. In a study of twelve fatal cases, blood ethylene glycol concentrations ranged enormously, from 58 to nearly 7,800 mg/L, while glycolic acid concentrations clustered in a much narrower range.15PubMed. Ethylene glycol and glycolic acid in postmortem blood from fatal poisonings
A larger study of fatal cases found that glycolic acid concentration in the blood, rather than ethylene glycol itself, was the better marker for identifying a fatal poisoning, with an approximate threshold around 1.5 g/L. Urine turned out to contain substantially higher concentrations of both compounds than blood, with median urine-to-blood ratios of roughly 3 to 4, making it a valuable screening sample when poisoning is suspected.16PubMed. Ethylene Glycol and Metabolite Concentrations in Fatal Ethylene Glycol Poisonings Pathologists also look for calcium oxalate crystals in kidney tissue under polarized light, a finding that was consistently present in fatal cases across both studies.
Pets Are Far More Vulnerable
Dogs and cats are notoriously susceptible to ethylene glycol poisoning, and not because they encounter it in larger doses than humans. Cats are especially sensitive: a lethal dose in a cat can be as low as 1.5 mL per kilogram, meaning just a tablespoon or so of antifreeze could kill an average-sized cat. Dogs are somewhat more tolerant but still at grave risk from puddles of spilled coolant. A retrospective study of fifty dogs and cats with confirmed ethylene glycol poisoning found that 78% died, largely because of delays in getting the animals to treatment.17Journal of the American Veterinary Medical Association. Clinicopathologic findings in dogs and cats with ethylene glycol intoxication
The same metabolic pathway operates in animals: alcohol dehydrogenase converts ethylene glycol to glycolate and eventually to oxalic acid, which destroys the kidneys. Fomepizole can be used in dogs but is less effective in cats, who metabolize ethylene glycol differently. The window for successful treatment is extremely narrow in cats, often just a few hours. For pet owners, the practical takeaway is that any suspected exposure, even a lick of a wet garage floor, warrants an immediate trip to a veterinary emergency clinic.
Do Bittering Agents in Antifreeze Actually Help?
Many antifreeze manufacturers now add denatonium benzoate, one of the most bitter-tasting substances known, to their products. The idea is intuitive: make antifreeze taste horrible so that children and pets will spit it out rather than swallow it. Several U.S. states have passed laws requiring the addition of a bittering agent to consumer antifreeze.
The evidence that this works is, frankly, disappointing. A large analysis of ethylene glycol exposure reports in the United States found that the addition of denatonium benzoate was not associated with any reduction in the number of exposures or in their severity.18PubMed Central. Clinical Features of Reported Ethylene Glycol Exposures in the United States A separate study focused specifically on children found the same thing: after Oregon and California mandated bittering agents, the frequency of pediatric antifreeze ingestions did not change, nor did the volume swallowed, the severity of symptoms, or the rates of hospitalization and intensive treatment.19PubMed. The impact of bittering agents on pediatric ingestions of antifreeze The reasons likely include that most serious poisonings are intentional (self-harm or harm to others), and that even among accidental exposures, a child or pet may swallow enough before the bitterness registers. Bittering agents are not harmful, so there is little reason not to add them, but they should not be treated as a reliable safety net.
The 1937 Disaster That Changed Drug Safety Law
Ethylene glycol’s close chemical relative, diethylene glycol, was the cause of one of the most consequential pharmaceutical catastrophes in American history. In 1937, a company formulated a liquid version of the antibiotic sulfanilamide using diethylene glycol as the solvent. At the time, no law required drug manufacturers to test their products for safety before selling them. One hundred and five people, many of them children, died after taking the preparation. The public outrage that followed directly led to the passage of the 1938 Federal Food, Drug and Cosmetic Act, which for the first time required proof of safety before a drug could be sold in the United States.20PubMed. Elixirs, diluents, and the passage of the 1938 Federal Food, Drug and Cosmetic Act
Diethylene glycol is not the same compound as ethylene glycol, but they are metabolized through similar pathways and produce overlapping toxic effects, including severe kidney damage. The 1937 tragedy is a reminder that glycol toxicity is not a modern discovery or an obscure laboratory concern. It has shaped the regulatory framework for drug safety in ways that persist today, and diethylene glycol contamination continues to cause mass poisoning events in countries with weaker pharmaceutical oversight.