Since its introduction in the 1970s, total parenteral nutrition (TPN) has gained popularity as a means of nutritional support for patients who cannot orally ingest sufficient calories and nutrients to promote wound healing or recovery from debilitating illness. As this treatment modality is employed among heterogenous groups of patients, a number of potential problems have been identified. Fortunately, most of these difficulties can be eliminated or minimized by understanding the metabolic goals of TPN and by employing proper catheter management. One of the unusual complications, a high anion gap metabolic acidosis refractory to bicarbonate therapy, occurred in one of our patients who was receiving TPN without adequate thiamine supplementation. The casual relationship between thiamine deficiency and metabolic acidosis has been well described in the literature, but remains under-recognized by many physicians.