- Patients with alcohol use disorder frequently have a thiamine deficiency.- A potential life-threatening complication of thiamine deficiency is Wernicke's encephalopathy.- Since it is clinically difficult to recognize Wernicke's encephalopathy, this condition is often treated inadequately. - Early supplementation of thiamine is important to avoid irreversible neurological damage. - There are differences between the Dutch guidelines regarding the supplementation of thiamine for the treatment of alcoholic use disorder, and those for Wernicke's encephalopathy. - There are no solid evidence-based recommendations about the best dosage, route of administration and duration of thiamine supplementation for the treatment of alcohol use disorder and Wernicke's encephalopathy. - Based on the pharmacokinetic properties of thiamine, it is more appropriate to give patients with alcohol use disorder 25 mg four times a day rather than 50 mg twice a day. - Patients at high risk of Wernicke's encephalopathy should immediately receive an intravenous or intramuscular dose of thiamine; patients with suspected Wernicke's encephalopathy should preferably receive an intravenous dose.- Reports of anaphylactic reaction to parenteral administration of thiamine are rare and are not a reason to refrain from parenteral treatment.