For patients on metformin having intravenous iodinated contrast, routine withholding is not needed when eGFR is 30 mL/min/1.73 m² or above and there is no acute kidney injury. The risk of lactic acidosis lies with severe or acute kidney impairment, not with contrast itself. For patients with eGFR below 30 or acute kidney injury, withhold metformin at the time of contrast and for 48 hours afterwards, restarting once kidney function is confirmed stable.
- Check a recent eGFR and ask about acute illness before contrast in patients on metformin.
- Continue metformin when eGFR is 30 or above without acute kidney injury.
- Withhold metformin for 48 hours when eGFR is below 30 or kidney injury is acute.
- Recheck kidney function before restarting metformin in those who stopped it.
Why it matters
Unnecessary withholding disrupts glucose control and delays scans for many patients with normal kidneys.
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