We describe herein a case of thyroid storm with hypoglycemia and lactic acidosis—a rare complication of thyroid storm. The patient was a 50-year-old Japanese woman who suffered cardiopulmonary arrest an hour after hospitalization. Analysis of a blood sample obtained before her cardiopulmonary arrest yielded surprising results: Her plasma glucose level was 14 mg/dL and her lactic acid concentration had increased to 6.238 mM. Thus, if atypical thyroid storm presents with normothermic hypoglycemia, and lactic acidosis, we believe it is necessary to consider a diagnosis of thyroid storm earlier, because this condition requires emergency treatment. Moreover, it is very important to apply standard principles in the treatment of atypical cases of thyroid storm.