Thiamin deficiency (TD) can lead to beriberi and multi-organ failure. Despite its low prevalence in the industrialized world, TD remains a major health problem in developing countries, esepcially those in Asia. The purpose of this review was to examine the epidemiology, pathophysiology, clinical characteristics, and laboratory test of thiamin deficiency. Related literature was identified using keywords "thiamin" or "thiamin deficiency" to search PubMed. The diagnosis of TD is based on clinical symptoms and and laboratory test results. Thiamin infusion alleviates symptoms effectively only for patients with thiamin deficiency. It is also noted that symptoms of TD might be aggravates when diuretic was used. Patients with poor nutritions, heart failure, diabetes, long-term parenteral infusion or surgical intervention for obesity are at high risk of thiamine deficiency. Adequate nutritional supplement for them should be ensure.