After taking 15 mg of pioglitazone daily for 4 months and 30 mg daily for 2 months, the patient developed abdominal pain, nausea, loss of appetite, and weight loss. Results of blood tests, including tests of liver function, were normal. He developed high blood sugar, and his doctors increased the daily pioglitazone dose to 45 mg. Several days later, the patient noticed that the whites of his eyes were turning yellow and his bowel movements were light in color. He had another set of liver function tests, which showed liver damage. Pioglitazone was stopped, but he continued to take his other medications. Extensive tests revealed no other potential causes of liver damage, and a biopsy of the liver showed changes compatible with drug-related liver damage. The patient's symptoms gradually improved, and results of liver tests became normal 6 weeks after the pioglitazone was stopped.