Metformin

Perioperative metformin recommendations differ between guidelines.

ADA 2026

The recommendation is to hold metformin and other oral glucose-lowering agents on the day of surgery/procedure.

AHA/ACC 2024

The cardiovascular guidance states that continuation of metformin during the perioperative period is reasonable in patients with diabetes or impaired glucose tolerance.

Why the concern exists

The historical concern is metformin-associated lactic acidosis. It is rare, and risk is linked mainly to conditions that impair lactate clearance or cause hypoperfusion, such as significant renal impairment, hepatic impairment, shock, hypoxaemia and major haemodynamic instability.

Applying the guidance

These recommendations differ. Individual planning takes account of the applicable institutional protocol, renal function, contrast exposure, haemodynamic status, glycaemic needs and the planned procedure. Factors that may favour interruption include:

Reduced or unstable renal function
Planned intravascular iodinated contrast, applied according to the current contrast guidance and eGFR
Major surgery with expected haemodynamic instability or fluid shifts
Bowel preparation or anticipated dehydration

In short procedures with minimal disruption to eating, continuation may be reasonable under some protocols.

Restarting

Resumption is usually considered when oral intake and clinical condition have recovered and renal function is stable. After iodinated contrast, the applicable contrast guidance and any required renal assessment inform the timing.