The current guidelines contain substantial inconsistency regarding the use of metformin concomitantly with contrast media. The objective of this study is to appraise the guidelines and summarize the agreements and differences among recommendations. Our search focused on English language guidelines published between 2018 and 2021. Guidelines for the management of contrast media in patients with continuous metformin were included. Guidelines were assessed using the Appraisal of Guidelines for Research and Evaluation II instrument. Six guidelines out of 1134 fulfilled the inclusion criteria with an AGREE II score of 79.2% (IQR 72.7 to 85.1%). There was good overall quality of the guidelines, with six considered "strongly recommended." CPGs scored poorly in "Clarity of Presentation" and "Applicability," with scores of 75.9% and 76.4%, respectively. The intraclass correlation coefficients were excellent in each domain. There are some guidelines (33.3%) that recommend discontinuation of metformin in patients with an eGFR of < 30mL/min/1.73 m2, while some guidelines (16.7%) suggest the threshold of renal function should be eGFR < 40mL/min/1.73 m2. Most guidelines recommend withdrawing metformin before using contrast agents in diabetic patients with severely impaired kidney function but disagree on the renal function thresholds. Furthermore, the gaps regarding discontinuing metformin with moderate renal impairment (30mL/min/1.73 m2 < eGFR < 60mL/min/1.73 m2) must be considered in future studies. • Guidelines involving metformin and contrast agents are reliable and optimal. • Most guidelines advocate discontinuing metformin before using contrast agents in diabetic patients with advanced renal failure, but there are controversial suggestions regarding kidney function thresholds. • The gaps regarding the time of discontinuation of the metformin with moderate renal impairment (30mL/min/1.73 m2 < eGFR < 60mL/min/1.73 m2) must be considered in the extensive RCT studies.
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