Metformin rarely produces hypoglycemia (low blood sugar levels) because it does not change how much insulin is secreted by the pancreas and does not cause high insulin levels. But metformin toxicity or overdosage that causes lactic acidosis has been associated with hypoglycemia. Experts believe the cause may be increased glucose consumption due to anaerobic metabolism, coupled with a decreased oral intake of food and carbohydrates, decreased liver glucose production, and decreased glucose absorption.

The combination of metformin with a persistently poor diet or other medications that can cause hypoglycemia, such as sulfonylureas, can also lead to hypoglycemia.

When metformin is taken as directed by a doctor it does not cause hypoglycemia.