The purpose of this study was to establish guidelines on how to avoid metformin-induced lactic acidosis following intravascular use of contrast media. We reviewed articles published in international journals. No conclusive evidence was found to indicate that the intravascular use of contrast media precipitated the development of metformin-induced lactic acidosis in patients with normal S-creatinine (< 130 mumol/l). The complication was almost always observed in non-insulin-dependent diabetic patients with decreased renal function before injection of contrast media. Guidelines for the use of contrast media in this group of patients are proposed.