Metformin is a prescription medication used to treat the symptoms of Type 2 Diabetes Mellitus. Learn about side effects , dosages, drug interactions, and more. Learn about the possible side effects of metformin , a common diabetes medication, such as lactic acidosis, hypoglycemia, gastrointestinal issues, and more. Find out how to prevent, reduce, or report these side effects and when to seek medical attention. Metformin is one of the most prescribed drugs on the planet, but the side effects can be tough. Here's what you can do to avoid metformin side effects . Metformin commonly causes side effects like nausea, diarrhea and bloating . More serious side effects involve low blood pressure and lactic acidosis.