Metformin, a medication used to lower glucose levels in patients with diabetes mellitus, has long been thought to increase the risk for a metabolic disorder known as lactic acidosis. An antecedent phenformin therapy was performed in fifteen cases and was associated with renal insufficiency in ten cases and liver disease in eight cases. Whatever the underlying cause, unchecked metabolic acidosis can kill an affected individual. She was admitted in for her fifth cycle of chemotherapy. The results showed that grapefruit juice alone, or in combination with metformin, lowered blood glucose levels. Lactic acid levels can also get higher when the liver is severely damaged or diseased, because the liver normally breaks down lactic acid. The product label for XIGDUO XR contains a boxed warning for lactic acidosis, a rare, but serious metabolic complication that can occur due to metformin accumulation during treatment with XIGDUO XR.