Methanol toxicity (also methanol poisoning) is poisoning from methanol, characteristically via ingestion. Symptoms may include an altered/decreased level of consciousness, poor or no coordination, vomiting, abdominal pain, and a specific smell on the breath. Decreased vision may start as early as twelve hours after exposure. Long-term outcomes may include blindness and kidney failure. Ingestion of as little as 3.16 grams of methanol can cause irreversible optic nerve damage, and the oral LD50 for humans is estimated to be 56.2 grams.
Methanol poisoning most commonly occurs following the drinking of windshield washer fluid. This may be accidental or as part of an attempted suicide. Toxicity may also rarely occur through extensive skin exposure or breathing in fumes. When the body breaks down methanol it results in the creation of metabolite byproducts such as formaldehyde, formic acid, and formate which cause much of the toxicity. The diagnosis may be suspected when there is acidosis or an increased osmol gap and confirmed by directly measuring blood levels. Other conditions that can produce similar symptoms include infections, exposure to other toxic alcohols, serotonin syndrome, and diabetic ketoacidosis.