Metformin is a widely used antihyperglycemic agent recommended by both the American Diabetes Association and the European Association for the Study of Diabetes as the first-line type 2 diabetes treatment in all patients receiving a new diagnosis, regardless of age Lactic acidosis (LA) is a rare event, with an estimated incidence of 4.3 cases per 100,000 person-years in metformin users LA is caused by the buildup of lactic acid in the bloodstream. It is characterized by an arterial lactate level ?5 mmol/L and a blood pH ?7.35, and occurs when oxygen levels in the body drop (hypoxia). The occurrence of LA in type 2 diabetes is of great concern because the mortality rate of LA can be as high as 50% .To determine whether the use of metformin in type 2 diabetic patients with various kidney functions is associated with an increased risk of lactic acidosis (LA). Lactic acidosis occurs in patients taking metformin who have renal failure. In our study, metformin was used in CKD stage 1 to 3b patients. Most of them were in stage 3. There is statistically significant association between stages of kidney disease and serum lactate level(P<0.05) .There Is statistically significant association between stages of kidney disease and arterial blood gas analysis.