Elevated lactate levels are associated with acute illnesses, and the mortality is high. Here, we report a case of lactate-containing peritoneal dialysis (PD) solution inducing lactic acidosis corrected by changing to hemodialysis (HD). This 70-year-old female patient was treated with PD 8 months previously for end-stage renal disease caused by diabetes mellitus. She was admitted complaining of general weakness. Initial lactate level was 22.1 mg/dL and increased to 62.4 mg/dL showing high anion gap metabolic acidosis and compensatory hyperventilation. There are no definite causes of lactic acidosis besides the use of PD solutions containing a lactate component. The patient's lactate level was decreased after temporarily changing the dialysis modality to HD. Her lactate level was increased again after restarting PD, and decreased to normal after restarting HD. We report this case because physicians should consider lactate-containing PD solution as a possible cause of lactic acidosis.