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It is variable. About 60–240 ml is fatal. But, even 30–60 ml have proved fatal and recovery has occurred after absorption of 500–600 ml of absolute methanol.

The smallest amount reported to cause death is 15 ml of 40% methanol and 4 ml is the lowest recorded toxic dose.

Fatal period
Usually 24–36 hours. But, may be delayed for 3–4 days.

Signs and Symptoms of Methanol Consumption
Signs and symptoms vary according to

Onset of symptoms is prolonged – as long as 24-36 hours – when sufficient toxic metabolites have accumulated


Impairment of vision due to methyl alcohol intoxication is abrupt in onset. And if visual functions return, it generally does so in the first six days.

This has prognostic significance. No patient with normally reactive pupils has suffered permanent visual loss. However, the decreased pupillary reaction may occur in patients who have had a complete recovery.

The mechanism of selective involvement of the optic nerve in methanol toxicity remains unknown.

Other drugs with proven but less devastating toxic effects on the optic nerve include

These above features are accompanied by

Despite severe acidosis, “Kussmaul Respiration” (i.e. intense hyperventilation or air hunger) is not common because of respiratory depression caused by intoxication. In moribund patients, the respiration is slow, shallow, gasping and “fish–mouth”.

Coma follows unconsciousness and death occurs from cardiorespiratory failure and is almost always preceded by blindness.