Every physician knows that alcohol dependence, alcohol withdrawal and Wernicke-Korsakow-syndrome require substitution with thiamine, in acute stages even parenterally. This would be trivial if there was not the widespread fear of anaphylactic, even lethal reactions to parenteral thiamine application. The present article reviews the literature published on thiamine since 1936, when the first synthetic, parenteral thiamine preparation became available, and, on this basis, tries to give practical advice and therapeutic regimens for the treatment of thiamine deficiency states. Controlled clinical studies on indications and differential thiamine therapy have not been published. From the data that are available, the following conclusions can be drawn: 1) Acute mortality of Wernicke-Korsakow-syndrome is about 20%. 2) Oral thiamine is safe. 3) The risk for an anaphylactic shock due to parenteral thiamine administration is below 1 to 100,000. 4) Not only alcohol but any condition with either increased metabolic need (pregnancy, consuming diseases) or deficient nutrition (including eating disorders) can lead to thiamine deficiency. Therefore, we suggest: 1) Oral thiamine substitution with at least 50 mg per day and supply of a sufficient and complete diet should be given to any person that might be at risk for thiamine deficiency. 2) Any patient suspicious for acute thiamine deficiency needs to be treated under inpatient conditions and there needs to receive 50 to 100 mg thiamine intravenously 3 to 4 times a day. 3) General practitioners, psychiatrists and neurologists should take care of the oral supplementation of thiamine, sufficient nutrition, and they are the physicians to diagnose early stages of thiamine deficiency.