By the BossCE Editorial Team · 10 November 2026

The Short Answer

Guidelines disagree when eGFR is between 30 and 60 mL/min/1.73m². Some say metformin can continue; others advise a temporary stop. Many clinicians take the cautious route because of the rare but serious risk of metformin-associated lactic acidosis.

What Each Guideline Says

• ACR (American College of Radiology): with eGFR 30 or above and no acute kidney injury, metformin does not need to be stopped before or after intravenous iodinated contrast.
• RANZCR (Royal Australian and New Zealand College of Radiologists): continue metformin if eGFR is above 30; stop for at least 48 hours only if eGFR is below 30, unknown, or the patient is unwell or renal function is deteriorating.
• ESUR (European Society of Urogenital Radiology): if renal function is abnormal, stop metformin from the time of the study and do not restart for 48 hours, and only if renal function is stable.
• US FDA label: stop metformin at or before contrast in patients with eGFR 30 to 60 (and in some other groups), recheck eGFR at 48 hours, and restart if renal function is stable.
• NICE: with eGFR below 60, decide with the referring clinician whether to withhold metformin for 48 hours, with renal function checked before restarting.

If You Stop It

Stop metformin at the time of, or just before, the contrast study, withhold it for 48 hours, and restart only after eGFR has been rechecked and is stable or back to baseline.

Sources Behind This Summary

ACR Manual on Contrast Media; RANZCR guidance; ESUR guidelines; US FDA metformin labelling; NICE; supporting hospital and academic sources numbered in the full BossCE AI answer.

Summarised on 10 November 2026 from a BossCE AI answer with numbered sources. For qualified clinicians: it does not replace clinical judgement or local protocols. Spotted something out of date? Tell us.