Lactic acidosis after contrast in patients on metformin is rare, and the risk is concentrated in those with poor or acutely worsening kidney function. Current ACR guidance does not require metformin to be stopped in patients with an eGFR of 30 or more and no acute kidney injury.
For patients with an eGFR below 30, or with acute kidney injury, metformin is withheld at the time of contrast and for 48 hours afterwards, restarting once renal function is confirmed stable. Blanket stopping for every patient delays scans and disrupts diabetes control without benefit.
- Check a recent eGFR before contrast in patients on metformin
- Continue metformin when eGFR is 30 or more and there is no acute kidney injury
- Withhold metformin for 48 hours after contrast when eGFR is below 30 or kidney function is acutely worsening
- Restart after renal function is confirmed stable
Why it matters
Unnecessary metformin holds delay imaging and disrupt glucose control.
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