Thiamine is the cofactor of many enzymes involved in energy metabolism. Patients under total parenteral nutrition are at risk for thiamine deficiency if there is renal thiamine loss or increased thiamine requirements to mitigate systemic diseases. Thiamine deficiency symptoms include seizures, neuropathy, ataxia, peripheral vasodilation, myocardial insufficiency, sudden collapse, and death. In this report, we present an infant liver transplant recipient with progressive lactic acidosis that responded well to thiamine replacement to mitigate a lack of thiamine in total parenteral nutrition.