由嚴重急性呼吸道症候群冠狀病毒2 型(severe respiratory syndrome coronavirus 2) 所引起的2019 年新型冠狀病毒感染症(coronavirus disease 2019, COVID-19)，是一種前所未有並具高度傳染力的病毒性疾病，已為全球帶來嚴峻的挑戰。高盛行率的糖尿病已成為COVID-19感染的其中一種最常見的共病症。許多研究指出糖尿病與COVID-19 感染結果是具有相關性的。血糖管理的好壞會影響到COVID-19 感染的預後與結果，相對於控制不佳的血糖而言，良好的血糖控制會有比較低的死亡率。許多研究顯示COVID-19 感染會導致高血糖、代謝功能異常、增加小血管之併發症與內皮細胞功能異常的環境之下增加血栓事件的發生。二甲雙胍類是最常使用的降血糖藥物，它除了具有降低血糖的功能之外，許多研究顯示它還具有其它多樣性效應，譬如說：抗感染、抗發炎、免疫調節、降血壓、預防慢性阻塞性肺疾病和心臟衰竭等。因此，二甲雙胍類可以藉由這些多樣性效應的類似機轉或有助於減少在COVID-19感染後引發的發病率和死亡率。由此觀點，二甲雙胍類可以考慮重新使用來應付日益增加感染COVID-19 之糖尿病人的一個可行性之選擇用藥。本篇綜論旨在整理二甲雙胍類的多重潛在性的機轉，透過這些分子機轉呈現可能有益於COVID-19 感染的治療效果，並且概括真實世界資料以支持重新思考使用二甲雙胍類在第二型糖尿病人併有COVID-19 感染的益處。

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has posed a remarkable global challenge as a previously unrecognized viral infection with high infectivity. The high prevalence of diabetes makes it one of the most common comorbidities observed in patients with COVID-19 infection. Studies have suggested that diabetes is associated with unfavorable COVID-19-related outcomes. Lower mortality rates have been observed among individuals with good glycemic control than among those with poor glycemic control, and glycemic management may affect the prognoses and outcomes of COVID-19 infection. Several studies have demonstrated that COVID-19 infection contributes to hyperglycemia, metabolic dysfunction, and increased microvascular complications and thrombotic events against the backdrop of aberrant endothelial function. Metformin, the most prescribed oral antidiabetic medication, exhibits multiple beneficial effects beyond its glucose-lowering functions, such as anti-infection, anti-inflammation, immunomodulation, anti-hypertension, preventive effects on chronic obstructive pulmonary disease and heart failure. Hence, metformin may share similar mechanisms of these pleiotropic benefits or contribute to the reduced morbidity/mortality in COVID-19 infection. Therefore, metformin is a feasible candidate drug for repurposing to address the rising number of patients with COVID-19 infection who have diabetes. This review article presents a summary of the multiple potential mechanisms through which metformin produces beneficial therapeutic effects and summarizes real-world data supporting the repurposing of metformin for use in patients with COVID-19 who have type 2 diabetes.