Metformin, or Glucophage, is a drug commonly used to treat type 2 diabetes mellitus. It is available in both short and long-acting forms. RxList reports the most common side effects associated with metformin, occurring in more than 5 percent of patients using the drug, are diarrhea, nausea, vomiting, flatulence, diffuse lack of strength, headache, indigestion and abdominal discomfort. Metformin-induced renal side effects are rare but can be lethal.
Metformin is excreted out of the body by the kidneys. When the kidneys are not functioning properly, metformin can accumulate in high concentrations which may result in lactic acidosis. Lactic acidosis is a rare, serious metabolic abnormality that occurs with uncontrolled diabetes, severe hypotension as well as high metformin levels. According to Drugs.com, metformin-induced lactic acidosis is fatal in more than 50 percent of cases and usually occurs in diabetic patients with significant kidney dysfunction. Metformin should be used with great caution in patients with chronic renal disease and should be temporarily discontinued for surgery or procedures requiring radiocontrast agents. Symptoms of lactic acidosis are usually nonspecific but may include hypothermia, hypotension and a slow heart rhythm. Lactic acidosis always mandates immediate hospitalization with intensive supportive care and usually hemodialysis.
Acute Renal Failure
Acute renal failure is characterized by the kidneys' inability to filter toxins out of the blood as a result of injury to the kidney. There are numerous causes of acute renal failure but one of the more common is dehydration. Gastrointestinal side effects are common with metformin therapy and significant diarrhea or vomiting, particularly when there is underlying chronic renal disease, can lead to severe dehydration and acute renal failure. Discontinuation of metformin and vigorous rehydration usually results in restoration of baseline kidney function.
Not all renal side effects of metformin use are detrimental. Proteinuria, or albuminuria, is a condition in which the kidney is abnormally excreting protein into the urine. Proteinuria is a hallmark of kidney damage and diabetes is one of the main culprits. In a 2008 article in the "American Journal of Hypertension," Cubedda and colleagues reported that the combination of metformin along with a healthy lifestyle may reduce the amount of proteinuria seen in diabetes.