What are the current guidelines for patients taking metformin and needing a contrast study?

What are the current guidelines for Metformin and Iodinated Contrast agents? Classic recommendations: "U.S. Food and Drug Administration (FDA) guidelines for metformin advise that for patients in whom an intravascular contrast study with iodinated materials is planned, metformin should be temporarily discontinued at the time of or before the study, and withheld for 48 hours after the procedure and reinstituted only after renal function has been re-evaluated and found to be normal. " ACR Committee on Drugs and Contrast Media Guidelines on Metformin and Iodinated Contrast Agents The Committee recommends that patients taking metformin be classified into one of three categories, each of which has slightly different suggested management. Category I In patients with normal renal function and no known comorbidities (see Table B), there is no need to discontinue metformin prior to intravenously administering iodinated contrast media, nor is there a need to check creatinine following the test or procedure. Category II In patients with multiple comorbidities who apparently have normal renal function, metformin should be discontinued at the time of an examination or procedure using IV iodinated contrast media and withheld for 48 hours. Communication between the radiologist, the health care practitioner, and the patient will be necessary to establish the procedure for reassessing renal function and restarting metformin after the contrast-enhanced examination. The exact method (e.g., serum creatinine measurement, clinical observation, hydration) will vary depending on the practice setting. A repeat serum creatinine measurement is not mandatory.If the patient had normal renal function at baseline, was clinically stable, and had no intercurrent risk factors for renal damage (e.g., treatment with aminoglycosides, major surgery, heart failure, sepsis, "repeat administration of large amounts of contrast media), metformin can be restarted without repeating the serum creatinine measurement. Category III In patients taking metformin who are known to have renal dysfunction, metformin should be suspended at the time of contrast injection, and cautious follow-up of renal function should be performed until safe reinstitution of metformin can be assured.  Per ACR Manual on Contrast Media  Version 9 (2013)