The present study discusses the metabolism of ethanol in the human body from the ingestion of ethanol to the excretion of its break down products water and carbon dioxide. Ethanol is a small molecule, soluble in water as well as in organic solutions. It is quickly distributed to every section in the body, where it exerts a direct toxic effect on the cells. Ethanol cannot directly leave the body efficiently so it needs other metabolic pathways. The molecule is metabolized by oxidation, predominately in the liver. The enzyme alcohol dehydrogenase catalyses the degradation of ethanol to acetaldehyde. Acetaldehyde is even more toxic than ethanol and it is degraded by the enzyme aldehyde dehydrogenase. In chronic alcoholics other chemical processes such as the cytochrome P450 system may have a bigger impact on alcohol metabolism. The carbohydrate metabolism is extensively affected by ethanol. Most important is its restrictive effect on the gluconeogenesis leading to sustained hypoglycaemia in glycogen deprived alcoholics, possibly dangerous for the brain. Ethanol even affects the lipoprotein metabolism leading to evaluated plasma levels of HDL and triglycerides in alcoholics. The study also evaluates the genetic polymorphism of the enzymes alcohol dehydrogenase and aldehyde dehydrogenase, metabolic markers for high chronic ethanol consumption, ethanol as an energy supply, ethanol in medical treatment and harmful effects of ethanol and its metabolites on import organ systems in primarily alcoholics.