Results of a large-scale study suggest that the oral diabetes drug metformin is safe for most diabetics who also have chronic kidney disease (CKD). The study of more than 150,000 adults by Johns Hopkins Medicine investigators found that metformin’s association with the development of a life-threatening condition called lactic acidosis was seen only among patients with severely decreased kidney function.

A report on the study appeared online June 4 in JAMA Internal Medicine.

Metformin is the first-line medication for treatment of type 2 diabetes in adults and the fifth most commonly used drug in the United States. However, there has been a longstanding concern in the medical community about prescribing metformin for people with both diabetes and CKD because it may cause lactic acidosis, says senior study author Morgan Grams, MD, PhD, MHS, an associate professor of medicine and epidemiology at the Johns Hopkins University School of Medicine. Lactic acidosis is a rare but serious complication, occurring when lactate—a product of glucose breakdown—builds up in the bloodstream, producing symptoms such as severe muscle pain, cramps, nausea, and weakness. Because patients with CKD may be at increased risk of metformin-associated lactic acidosis, health-care providers historically avoided prescribing metformin in this population.