# Ethylene Glycol Toxicity

Treat suspected ethylene glycol poisoning before confirmatory levels return when exposure history, high-anion-gap acidosis, osmolar gap, or oxalate crystalluria indicates evolving toxic metabolite production; use fomepizole promptly and add hemodialysis for acidosis, renal failure, or severe measured exposure.

**Clinical question:** How should physicians diagnose, antidote-treat, dialyze, and monitor suspected ethylene glycol poisoning?

Updated: 2026-09-16T00:03:03.507860+00:00

## What matters in practice
- Do not await a confirmatory ethylene glycol concentration when suspicion is supported by exposure history, high-anion-gap metabolic acidosis, increased osmolar gap, or urinary oxalate crystals; start fomepizole immediately. [1][2]
- A documented serum ethylene glycol concentration greater than 20 mg/dL is an indication for fomepizole; the labeled regimen is 15 mg/kg IV once, then 10 mg/kg IV every 12 hours for four doses, then 15 mg/kg IV every 12 hours. [1][5][15]
- Add hemodialysis for renal failure, significant or worsening metabolic acidosis, or an ethylene glycol concentration of at least 50 mg/dL. [1][2]
- An elevated anion gap plus elevated osmolar gap and calcium oxalate or hippurate crystalluria strongly supports ethylene glycol poisoning, but absent urinary crystals do not exclude it. [18]
- Follow serial acid-base status and ethylene glycol concentrations during treatment because parent ethylene glycol declines as toxic metabolites accumulate; renal injury may emerge 24 to 72 hours after exposure. [1][15]

## When to treat suspected ethylene glycol toxicity immediately

Antidote decisions should be driven by exposure risk and evolving metabolic evidence, not symptom severity alone.

Begin fomepizole immediately if ethylene glycol ingestion is suspected from a credible history together with anion-gap metabolic acidosis, increased osmolar gap, urinary oxalate crystals, or a documented ethylene glycol concentration greater than 20 mg/dL. Do not wait for clinical deterioration or for a send-out concentration: untreated metabolism produces glycolic and oxalic acids and can progress to seizures, coma, acute tubular necrosis, and death. [1][2]

Obtain initial venous or arterial blood gas, basic metabolic panel, measured serum osmolality, glucose, BUN, ethanol concentration, urinalysis with microscopy, and a serum ethylene glycol concentration where available. Repeat acid-base and electrolyte measurements frequently during treatment; a falling parent-compound concentration does not establish safety if the anion gap or acidosis is worsening from accumulating metabolites. [1][18]

Admit patients receiving fomepizole, ethanol, or hemodialysis to an ICU-level setting. Give crystalloid for clinically important volume depletion from vomiting or osmotic diuresis, and correct severe acidemia while preparing antidote therapy and dialysis when indicated. [15][20]
- Call a poison center or medical toxicologist while antidote therapy and definitive laboratory testing are initiated; management depends on serial metabolic and concentration data. [1][24]
- Do not use absence of symptoms, a reportedly small ingestion, or absent crystalluria to defer treatment when laboratory findings support toxic alcohol exposure. [15][18]
- Activated charcoal, nasogastric lavage, and whole-bowel irrigation have no established role after ethylene glycol ingestion because absorption is rapid. [20]

*Immediate triggers for ethylene glycol-directed intervention. [1][2][20]*

| Finding | Interpretation | Immediate action |
| --- | --- | --- |
| Credible ingestion plus high-anion-gap metabolic acidosis, increased osmolar gap, or oxalate crystalluria | Presumptive ethylene glycol toxicity; toxic metabolite formation may already be occurring. [1][2] | Start fomepizole immediately; obtain serial blood gas, electrolytes, measured osmolality, urinalysis, and ethylene glycol concentration. [1] |
| Serum ethylene glycol >20 mg/dL | Meets labeled treatment threshold for fomepizole. [1][2] | Administer fomepizole; continue concentration and acid-base monitoring. [1] |
| Renal failure, significant or worsening metabolic acidosis, or ethylene glycol ≥50 mg/dL | Severe poisoning requiring consideration of extracorporeal toxin and metabolite removal. [1][2] | Arrange hemodialysis in addition to fomepizole. [1][2] |
| Refractory acidemia despite bicarbonate-based correction | Indicates failure of temporizing management and need for extracorporeal therapy. [20] | Initiate hemodialysis. [20] |

## How to interpret anion gap, osmolar gap, and urine microscopy

The diagnostic pattern changes with time because the parent alcohol is converted to organic acids.

Calculate the osmolar gap using measured osmolality minus calculated osmolality: 2 × sodium + BUN/2.8 + glucose/18 + ethanol/4.6 when ethanol is present. A normal osmolar gap is approximately -14 to +10 mOsm/L by this method. An increased osmolar gap supports unmeasured parent alcohol, whereas an elevated anion gap identifies accumulating acidic metabolites. [18]

The strongest bedside laboratory pattern is high-anion-gap metabolic acidosis with an elevated osmolar gap and urinary calcium oxalate or hippurate crystals. Calcium oxalate crystals may be dumbbell-, envelope-, or needle-shaped; needle forms are reported most commonly. Urine microscopy is supportive rather than exclusionary: renal damage can occur without crystal deposition or detectable crystalluria. [18]

Interpret gaps in the clinical time course. Early after ingestion, parent ethylene glycol can raise the osmolar gap before major acidosis develops. Later, ethylene glycol may have fallen as glycolate and oxalate rise, producing marked anion-gap acidosis with a less conspicuous osmolar gap. Therefore, neither a declining ethylene glycol concentration nor a single gap calculation should override worsening acidemia or kidney injury. [1][6]

A normal anion gap does not categorically exclude ethylene glycol toxicity. Rarely, concurrent bromide intoxication may artifactually lower the calculated anion gap and conceal the expected organic acidosis; retain diagnostic concern when the exposure history, osmolar gap, coma, or crystalluria is compelling. [19]
- Send serum ethylene glycol concentration to confirm exposure and guide duration of therapy, but begin antidote treatment from the presumptive clinical pattern. [1][2]
- Obtain urinalysis with microscopy early and repeat when suspicion remains high; absence of calcium oxalate crystals is nondiagnostic. [18]
- Measure an ethanol concentration because ethanol contributes to calculated osmolality and can alter interpretation of the osmolar gap. [18]

*Actionable interpretation of the evolving laboratory phenotype. [1][18][19]*

| Pattern | What it suggests | Management consequence |
| --- | --- | --- |
| Increased osmolar gap with minimal acidosis | Recent parent ethylene glycol exposure may precede substantial toxic metabolite accumulation. [18] | If exposure is credible, start fomepizole rather than waiting for acidosis or a confirmatory level. [1][2] |
| High anion gap metabolic acidosis plus increased osmolar gap | Strongly supportive pattern for ethylene glycol poisoning, especially with compatible history. [18] | Start fomepizole, obtain ethylene glycol level, and assess immediately for dialysis criteria. [1][2] |
| High anion gap metabolic acidosis plus calcium oxalate or hippurate crystals | Supports oxalate-generating ethylene glycol metabolism. [18] | Treat presumptively and monitor renal function and acid-base trajectory. [1][15] |
| Normal or modest osmolar gap with worsening acidosis | Parent compound may have been metabolized; a low osmolar gap does not establish low risk. [1][6] | Continue antidote-directed management and consider dialysis for significant or worsening acidosis. [1][2] |

## Fomepizole regimen and treatment endpoint

Fomepizole blocks alcohol dehydrogenase and prevents additional glycolate and oxalate generation.

Use fomepizole as the preferred alcohol dehydrogenase inhibitor when available. It competitively inhibits alcohol dehydrogenase, preventing formation of toxic metabolites from ethylene glycol; compared with ethanol, it has predictable pharmacokinetics, simpler administration, and avoids ethanol-related inebriation. [4][15]

Give fomepizole 15 mg/kg IV as a loading dose, followed 12 hours later by 10 mg/kg IV every 12 hours for four doses. After 48 hours, increase to 15 mg/kg IV every 12 hours because fomepizole metabolism increases with continued treatment. The pivotal prospective ethylene glycol study continued therapy until the plasma ethylene glycol concentration was below 20 mg/dL. [5][15]

If fomepizole is unavailable, ethanol can provide alcohol dehydrogenase blockade while fomepizole is obtained or the patient is transferred. Ethanol requires frequent concentration monitoring and dose adjustment and has clinically consequential adverse effects, including central nervous system depression, hypoglycemia, hypothermia, and agitation. [20][21]

Continue serial blood gas or acid-base assessment, serum electrolytes, renal function, and ethylene glycol concentrations during antidote therapy. Escalate to hemodialysis when acidosis becomes significant or worsens, renal failure develops, or the measured ethylene glycol concentration is at least 50 mg/dL. [1][2]
- Use the 15 mg/kg every-12-hour fomepizole maintenance dose after 48 hours; do not continue the initial 10 mg/kg schedule beyond four maintenance doses. [5][15]
- During hemodialysis, continue fomepizole; the need for altered dosing during dialysis should be coordinated with toxicology and dialysis services because the provided evidence establishes continued antidote treatment but does not specify a dialysis-adjusted regimen. [1]
- Do not use antidote therapy as a substitute for dialysis when renal failure, substantial or worsening acidosis, or a concentration of at least 50 mg/dL is present. [1][2]

*Fomepizole dosing and monitoring for ethylene glycol poisoning. [1][5][15]*

| Treatment phase | Fomepizole regimen | What to follow |
| --- | --- | --- |
| Loading dose | 15 mg/kg IV once. [5][15] | Baseline and serial acid-base status, electrolytes, renal function, measured osmolality, and ethylene glycol concentration. [1] |
| First 48 hours | 10 mg/kg IV every 12 hours for four doses after the loading dose. [5][15] | Anion gap and blood gas trend; worsening metabolic acidosis is a dialysis trigger. [1][2] |
| After 48 hours | 15 mg/kg IV every 12 hours. [5][15] | Continue frequent ethylene glycol concentrations and acid-base assessment. [1] |
| Stopping target | In the prospective fomepizole study, therapy continued until plasma ethylene glycol was <20 mg/dL. [5] | Confirm metabolic abnormalities are resolving and reassess renal function. [1][15] |

## When ethylene glycol poisoning requires hemodialysis

Hemodialysis removes ethylene glycol and toxic metabolites while rapidly correcting acid-base derangements.

Consider hemodialysis in addition to fomepizole for renal failure, significant or worsening metabolic acidosis, or a measured ethylene glycol concentration of at least 50 mg/dL. These criteria reflect the need to remove both the parent alcohol and metabolites while correcting life-threatening metabolic abnormalities. [1][2]

Do not delay dialysis for a repeat ethylene glycol concentration when acidemia remains refractory to correction, kidney injury is evolving, or end-organ injury such as hypotension or shock accompanies the poisoning. A practical endpoint is correction of acidosis together with closure of the osmolar gap or reduction of ethylene glycol concentration below 20 mg/dL. [20]

Continue frequent electrolyte and acid-base monitoring during and after dialysis because the procedure corrects metabolic abnormalities, while delayed kidney injury can become apparent over 24 to 72 hours. Persistent or new renal failure after clearance of ethylene glycol warrants ongoing renal replacement assessment. [1][15]
- Ethylene glycol concentration ≥50 mg/dL: add hemodialysis to fomepizole. [1][2]
- Significant or worsening metabolic acidosis: add hemodialysis even if a timely concentration is unavailable. [1][2]
- Renal failure or acidemia refractory to correction: proceed with hemodialysis. [1][20]
- Continue dialysis until acidosis is corrected and the osmolar gap has closed or ethylene glycol is <20 mg/dL. [20]

*Dialysis decisions in ethylene glycol toxicity. [1][2][20]*

| Clinical trigger | Why it matters | Dialysis objective |
| --- | --- | --- |
| Ethylene glycol ≥50 mg/dL | Meets labeled criterion for considering hemodialysis. [1][2] | Lower ethylene glycol concentration while maintaining alcohol dehydrogenase blockade. [1] |
| Significant or worsening metabolic acidosis | Signals toxic metabolite burden and may progress despite parent-compound decline. [1] | Correct acid-base disturbance and remove ethylene glycol metabolites. [1][2] |
| Renal failure | Oxalate-associated tubular injury can impair clearance and may emerge after exposure. [1][15] | Provide extracorporeal clearance and manage acute renal failure. [15] |
| Acidemia refractory to bicarbonate-based correction | Represents an absolute hemodialysis indication in the cited emergency protocol. [20] | Rapidly correct pH and clear toxic alcohol burden. [20] |

## Serial monitoring and disposition after initial stabilization

Treatment duration and level of care are determined by metabolic trajectory, toxin clearance, and delayed kidney injury.

Follow ethylene glycol concentrations and acid-base status at frequent intervals throughout treatment. Use the serial anion gap and blood gas, rather than a single concentration alone, to detect continuing toxic metabolite burden; ethylene glycol concentrations diminish as metabolism proceeds and may be misleadingly low in delayed presentation. [1][2]

Trend serum creatinine and urine output for at least the period in which delayed renal effects are expected, because renal injury typically develops 24 to 72 hours after poisoning. Acute renal failure requires hemodialysis. [15]

Patients requiring fomepizole, ethanol infusion, or hemodialysis require ICU admission. A patient with a significant ingestion history but no or mild symptoms still requires blood and urine testing and prompt treatment decisions rather than discharge based on an initially benign examination. [15]
- Repeat blood gas or acid-base assessment and serum electrolytes frequently while antidote therapy is active. [1]
- Continue serial ethylene glycol concentration monitoring when available; treatment in the prospective fomepizole study ended below 20 mg/dL. [5]
- Monitor creatinine and urine output for delayed acute kidney injury over 24 to 72 hours. [15]

*Monitoring targets after antidote initiation. [1][5][15]*

| Parameter | Reason to trend | Action if abnormal |
| --- | --- | --- |
| Blood gas and anion gap | Detects ongoing or worsening organic acidosis from toxic metabolites. [1] | Escalate to hemodialysis for significant or worsening metabolic acidosis. [1][2] |
| Serum ethylene glycol concentration | Guides confirmation and clearance assessment; parent concentration may decline as metabolism continues. [1] | Continue antidote therapy; a prospective study used <20 mg/dL as the treatment endpoint. [5] |
| Serum creatinine and urine output | Renal effects can develop 24 to 72 hours after exposure. [15] | Treat acute renal failure with hemodialysis. [15] |
| Measured osmolality and osmolar gap | Tracks unmeasured parent alcohol burden, particularly early in the course. [18] | Use with acid-base trajectory and toxin concentration; do not use a falling gap alone to rule out toxicity. [1] |

## References
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## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.