The incidence of diabetes in China is high, metformin as a common therapeutic drug, when sugar users need to use iodine contrast, what is the effect of taking metformin, and how to use it correctly? 1.What is the effect of contrast agent on metformin? Metformin causes lactate accumulation by inhibiting the conversion of lactate to glucose on the one hand. On the other hand, it inhibits gluconeogenic enzymes in the liver and affects lactate metabolism. Iodinated contrast agents are excreted through the kidneys, so if the kidneys are damaged after receiving iodinated contrast agents, the excretion of the drug can be delayed, which may cause the occurrence of lactic acidosis. Therefore, when using iodinated contrast agent, the timing of metformin use should be considered. 2.How to use metformin during contrast examination? (1) The Expert Consensus on Clinical Application of Metformin (2016 version) points out that for people with normal renal function, it is not necessary to stop using it before contrast, but it should be stopped for 48 to 72h after using contrast agent under the guidance of a doctor, and the drug can be continued after the renal function is normal on review; while for people with abnormal renal function, it should be temporarily stopped for 48h before using contrast agent, and after that it should be stopped for 48 to 72h, and the drug can be continued after the renal function is normal on review can continue to use the drug. (2) The Chinese T2DM Prevention and Control Guidelines (2017 edition) point out that metformin should be suspended during imaging, but the suspension time is not mentioned. (3) The relevant metformin instructions mention that the product should be temporarily suspended from before to 48 hours after the examination, until the renal function returns to normal and then the drug is used again. 3.What should I pay attention to when discontinuing metformin? Stopping metformin when using contrast agents may cause elevated blood glucose, glucose users need to adhere to the control of diet, active exercise, monitoring blood glucose, blood glucose elevation and fluctuations are not obvious glucose users can not need to adjust the use of hypoglycemic drugs; if blood glucose elevation or fluctuations are obvious, according to the condition of glucose users can be temporarily changed to insulin or other oral hypoglycemic drugs treatment.