Unit Converter
Methanol
(Toxic Alcohol – High Anion-Gap Metabolic Acidosis & Ocular Toxicity)
Synonyms
- Methanol
- Methyl alcohol
- MeOH
- Wood alcohol
- Wood spirit
- Toxic alcohol
Units of Measurement
- mmol/L
- µmol/L
- mg/L
- mg/dL
- mg/100 mL
- mg%
- µg/mL
Molecular Weight
32.04 g/mol
Unit Conversions
Molar ↔ Mass
1 mmol/L=32.04 mg/L1\ \text{mmol/L} = 32.04\ \text{mg/L}1 mmol/L=32.04 mg/L 1 mg/L=0.0312 mmol/L1\ \text{mg/L} = 0.0312\ \text{mmol/L}1 mg/L=0.0312 mmol/L
mg/dL ↔ mmol/L
1 mg/dL=10 mg/L=0.312 mmol/L1\ \text{mg/dL} = 10\ \text{mg/L} = 0.312\ \text{mmol/L}1 mg/dL=10 mg/L=0.312 mmol/L
µmol/L
1 mmol/L=1000 µmol/L1\ \text{mmol/L} = 1000\ \text{µmol/L}1 mmol/L=1000 µmol/L
µg/mL
1 µg/mL=1 mg/L1\ \text{µg/mL} = 1\ \text{mg/L}1 µg/mL=1 mg/L
mg%
\text{mg%} = \text{mg/dL}
Description
Methanol is a highly toxic industrial alcohol found in:
- Solvents
- Paint thinners
- Antifreeze/windshield washer fluids
- Illicit/adulterated liquor
Methanol itself has minimal toxicity, but its metabolites are extremely dangerous:
- Formaldehyde
- Formic acid (causes metabolic acidosis and optic nerve injury)
This leads to:
- High anion-gap metabolic acidosis
- Visual disturbances → blindness
- CNS depression
- Multi-organ failure
Methanol levels are used for diagnosis, monitoring severity, and guiding antidote therapy.
Physiological Role
Methanol is not produced endogenously in significant quantity.
Normal blood levels: undetectable.
Clinical Significance
HIGH Methanol
Symptoms
- Nausea, vomiting
- Blurred or “snowfield” vision
- Headache
- Confusion
- Hyperventilation (due to acidosis)
- Seizures
- Coma
- Blindness
- Death
Causes
- Accidental ingestion
- Suicide attempt
- Consumption of adulterated liquor
- Occupational exposure (rare)
Mechanism
- Methanol → formaldehyde → formic acid
- Formic acid → optic nerve toxicity + acidosis
LOW Methanol
- Normal state
- Healthy individuals have undetectable levels (<2 mg/L)
Reference Intervals & Toxic Levels
Normal
- < 2 mg/L (undetectable)
Potentially Toxic
- > 20 mg/dL (200 mg/L; 6.2 mmol/L)
→ Treat with fomepizole or ethanol
Severe Toxicity
- > 50 mg/dL (500 mg/L; 15.6 mmol/L)
→ High risk of acidosis & visual damage
Life-Threatening
- > 100 mg/dL (1000 mg/L; 31 mmol/L)
→ Urgent dialysis required
Hemodialysis Indications
- Methanol > 50 mg/dL
- Or pH < 7.25
- Or visual symptoms
- Or severe metabolic acidosis
Diagnostic Uses
- Confirm methanol poisoning
- Guide antidote dosing (fomepizole/ethanol)
- Determine need for dialysis
- Monitor treatment progress
- Part of toxic alcohol panel (ethylene glycol, methanol, isopropanol)
- Forensic & medicolegal investigations
Analytical Notes
- Sample: serum or plasma
- Gold standard: GC or GC–MS
- Avoid ethanol contamination
- Store in tightly sealed tubes (methanol evaporates)
- Osmolar gap may be high before acidosis develops
- Serum formate levels correlate better with severity
Clinical Pearls
- Methanol toxicity may be delayed 6–30 hours, especially if ethanol was co-ingested.
- Eye symptoms (“snowy vision”) are highly suggestive.
- Treat before results return if suspicion is high.
- Fomepizole halts toxic metabolism → prevents formic acid formation.
- Dialysis removes both methanol and formic acid.
Interesting Fact
Only 10 mL of methanol can cause permanent blindness.
30 mL can be fatal without treatment.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Toxic Alcohols
- AACT Methanol Poisoning Guidelines
- Mayo Clinic Laboratories - Methanol
- ARUP Consult - Toxic Alcohol Panel
- Goldfrank’s Toxicologic Emergencies
- MedlinePlus / NIH - Methanol Poisoning