Rethinking Thiamine in the Emergency Department: Why a Hi-Phy-Vi-Based “Suspect and Treat” Approach Matters in an Aging Society

Thiamine deficiency remains a clinically relevant yet frequently overlooked condition in modern emergency departments, particularly in aging societies such as Japan. Although traditionally regarded as a rare or historical disease, thiamine deficiency is not uncommon among emergency patients with high-risk backgrounds, including older adults, malnutrition, malignancy, chronic illness, diuretic use, gastrointestinal surgery, pregnancy-related vomiting, and social isolation. Despite its prevalence, diagnosis is often delayed or missed because of nonspecific presentations, reliance on incomplete classic triads, and dependence on laboratory confirmation that is neither rapid nor widely available in emergency settings. Importantly, thiamine deficiency represents a continuum of disease spanning early, nonspecific symptoms (including gastrointestinal complaints) to overt syndromes such as Wernicke encephalopathy (WE) and wet beriberi. While Wernicke encephalopathy and wet beriberi are well recognized, earlier and less familiar manifestations, such as gastrointestinal beriberi characterized by nausea, vomiting, anorexia, and abdominal discomfort, are easily misattributed to benign or self-limited conditions. Failure to recognize these early stages may allow progression to irreversible neurological or cardiac injury. In the emergency department, thiamine deficiency should therefore be approached as a diagnostic safety issue rather than a rare metabolic disorder. Clinical decision-making should prioritize history, physical examination, and vital signs (Hi-Phy-Vi) over delayed laboratory testing. Given the low cost and favorable safety profile of parenteral thiamine, a "suspect and treat" strategy based on clinical risk assessment is more appropriate than a "test and wait" approach. This editorial rethinks the role of thiamine in emergency care, emphasizing that early recognition and empiric treatment guided by bedside assessment can prevent diagnostic error and improve patient outcomes.