The ACR Manual on Contrast Media advises that patients taking metformin who have no acute kidney injury and an eGFR of 30 mL/min/1.73 m² or more do not need to stop metformin before or after intravenous iodinated contrast, and do not need repeat renal function testing afterwards.
Stopping metformin for 48 hours and rechecking creatinine is advised for patients with acute kidney injury or an eGFR below 30. Blanket withholding for everyone causes missed doses, poor glycaemic control and unnecessary blood tests, without evidence of benefit.
- Check the most recent eGFR and ask about acute illness before contrast in a patient on metformin.
- Continue metformin if eGFR is 30 or more and there is no acute kidney injury.
- Withhold metformin for 48 hours and recheck renal function if eGFR is below 30 or there is acute kidney injury.
- Write the instruction clearly on the request or report so wards and patients are not left guessing.
- Follow your local protocol where it differs, and discuss changes with the referring team.
Why it matters
Routine withholding is still common and adds blood tests and glucose disruption for no measurable gain.
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