When should metformin be held in relation to surgery?

Metformin should be held 24 hours before and 48 hours after surgery, primarily to minimize the risk of lactic acidosis, particularly in patients undergoing procedures that may involve significant stress, reduced oral intake, or alterations in renal function. Metformin is primarily excreted by the kidneys, and any impairment in renal function during the perioperative period could lead to accumulation of the drug, thus increasing the risk of lactic acidosis, which is a potentially life-threatening condition.

This approach is especially important in surgeries that could affect renal perfusion or in situations where the patient's hydration levels may be compromised due to fasting or fluid shifts. Holding metformin for this extended period helps ensure the patient’s safety, allowing time for kidney function to stabilize postoperatively before resuming the medication.

Other options suggest shorter or less comprehensive withholding periods, which do not align with safe practices regarding the use of metformin in the context of surgical events that add risk to renal function and overall patient safety.