Severe Perioperative Lactic Acidosis and Hyperglycemia Responsive to Thiamine in a Patient With Prior Semaglutide Use and Restrictive Dieting: A Case Report.

Thiamine deficiency is a rare but potentially fatal cause of type B lactic acidosis, classically associated with alcoholism or severe malnutrition. Restrictive dieting and weight-loss regimens, including glucagon-like peptide-1 (GLP-1) receptor agonist use, may unmask thiamine deficiency under perioperative stress. We report a young, nondiabetic woman on a restrictive diet who developed severe lactic acidosis and hyperglycemia after total abdominal hysterectomy, with worsening lactate despite hemodynamic stability and adequate hydration. Empiric intravenous thiamine produced rapid normalization of both lactate and glucose. Preoperative nutritional risk assessment and early empiric thiamine should be considered in similar perioperative presentations.