BACKGROUNDAs one of most widely-used biguanides, metformin can induce the lactic acidosis in patients with renal failure though its incidence is very low. However, lactic acidemia induced by metformin was reported in patients without renal dysfunction. It is unclear that whether lactatemia exists in diabetic patients with normal renal function in Chinese or not and its influencing factors. This study aimed to clarify the influencing factors of lactic acid, and identify a practiced clinical marker to predict the hyperlactacidemia in diabetics with normal renal function.

METHODSThe clinical data and venous blood samples of 1024 type 2 diabetic patients treated with (n = 426) or without metformin (n = 599) were collected. The lactic acid was assayed by enzyme-electrode method. The biochemical indexes included creatinine (Cr) and hepatase were measured with enzymatic procedures. The lactic acid concentrations of different Cr subgroups were compared, and the correlation and receiver operating characteristic curve analysis were used.

RESULTSThe mean lactic acid level and the proportion of hyperlactatemia of metformin group were significantly higher than that of non-metformin group (P < 0.01), but no lactic acidosis was found in all patients. The correlation and multiple stepwise regression analysis indicated that the correlative factors of lactic acid in turn were Cr, metformin, alanine transferase (ALT), body mass index (BMI), Urine albumin (Ualb), and blood urea nitrogen (BUN) in total patients; and Cr, ALT, BMI and BUN in non-metformin treated patients; Cr and ALT in metformin-group. The lactate concentration increased with the increment of Cr levels, and reached its peak at Cr 111-130 micromol/L, and the optimal cutoff of Cr in predicting hyperlactacidemia was 96.5 micromol/L.

CONCLUSIONSMetformin can increase the incidence of lactatemia in type 2 diabetic patients without renal dysfunction. Cr, ALT, and BMI are independent associated factors of blood lactic acid levels. There is low proportion of lactatemia in type 2 diabetics without metformin therapy, the optimal cutoff of Cr to predict lactatemia in these patients is 96.5 micromol/L.