Contrast-induced acute kidney injury is defined as a 25-50% or 0.3-0.5 mg/dl net increase in creatinine concentration compared to the baseline values. Metformin-associated lactic acidosis (MALA) is defined as an arterial pH (potential of hydrogen)<7.35 and plasma lactate concentration >5 mmol⁄L. In the M (-) group metformin will re-started 48 hours after angiography, albeit in the absence of evidence of lactic acidosis and GFR of >60 mL/min per 1.73 m2.