許多大型試驗的結果顯示，metformin除了降低血糖外，還有不增加體重、可預防大小血管併發症、及無低血糖風險等種種好處。根據目前歐美與我國各權威專科醫學會公布之第2型糖尿病治療指引，metformin一直是首選治療藥物。然而長久以來，與metformin相關的藥物不良反應(ADR) 如乳酸中毒(lactic acidosis)一直是臨床人員的憂慮。既有仿單與醫療行政機構明定諸多使用限制，其中腎功能不全( 男性血清肌酸酐(serum creatinine) ≥ 1.5 mg/dL、或女性血清肌酸酐≥ 1.4 mg/
dL) 更是明白數字規範。腎功能不全又是第2 型糖尿病常見的併發症，是以metformin雖屬首選又具優越療效之治療藥物，也可能隨時因肌酸酐濃度稍許波動而被停用，病人也因而可能衍生血糖失控問題。審慎地檢討限制因素之臨床意義是必要的。尤其決定腎功能不全的數據與切點，才可以免除乳酸中毒的顧忌又兼顧血糖控制。分析現有針對metformin、腎功能、與乳酸中毒間關係之臨床實證研究，可以瞭解何以近年來權威學術團體對腎功能不全漸趨一致地以eGFR＜30 ml/min訂為不建議使用metformin的切點。年齡因素事實上重點也是在eGFR，而不是年齡數字規範。Metformin 使用在心肺功能不全患者的研究仍有限，然而目前結果似乎也指向不須有過度嚴苛標準。

Many large-scale clinical studies demonstrated that metformin therapy had the beneficial effects of lowering blood sugar and preventing micro- and macrovascular complications. In addition, it had no risk of body weight gain and hypoglycemia. According to the current guidelines for the treatment of type 2 diabetes mellitus, metformin has been the first-line treatment of choice. However, metformin-associated lactic acidosis has long been a clinical concern. Both package insert of the manufacture and medical administrative bodies list many conditions as restrictions for metformin use. Of the restrictions, renal insufficiency (serum creatinine concentration ≥ 1.5 mg / dL for males, or ≥ 1.4 mg / dL for female) is the most well known. Under the condition of renal dysfunction, most clinicians would like to follow this regulation at the cost of glycemic control. Since renal insufficiency is a common complication in type 2 diabetes, metformin may be withdrawn at any time during the therapy. Thereafter, the new problem of poor glycemic control followed. Determining a critical level for renal insufficiency is very practical to avoid risk of lactic acidosis and
get the benefits of metabolic control. Reviewing study about metformin-associated lactic acidosis and renal function, most academic associations or societies consistently suggest eGFR <30 ml / min as the cut-off level that metformin should not be used. In elderly with type 2 diabetes, the key factor is eGFR value rather than the age itself. Although research about metformin use in patients with cardiac or pulmonary insufficiency is still limited, the recent data favor to relax these restrictions. (J Intern Med Taiwan 2014; 25: 1-6)