Metformin should generally not be taken for 48 hours after cardiac stenting because the procedure involves injecting an iodinated contrast agent into the blood vessels, and the combination of contrast agent and metformin can increase kidney damage, as well as cause metformin accumulation and increase the risk of lactic acidosis. Metformin is an oral hypoglycemic agent that lowers blood glucose by decreasing hepatic glucose output and increasing glucose utilization, primarily in type 2 diabetes. Metformin is contraindicated in patients with acute or chronic metabolic acidosis, severe renal failure, and decompensated heart failure, and should be withheld in patients using iodine contrast agents; therefore, metformin is generally not recommended within 48 hours after cardiac stenting. Patients should use metformin after cardiac stenting under medical supervision.