Association of metformin with susceptibility to COVID-19 in people with type 2 diabetes

Research output: Contribution to journalArticlepeer-review


External organisations

  • Queen Elizabeth Hospital Birmingham, Queen Elizabeth Medical Centre
  • University Hospitals Birmingham NHS Foundation Trust
  • University of Leicester


Diabetes has emerged as an important risk factor for mortality from COVID-19. Metformin, the most commonly prescribed glucose-lowering agent, has been proposed to influence susceptibility to and outcomes of COVID-19 via multiple mechanisms. We investigated whether, in patients with diabetes, metformin is associated with susceptibility to COVID-19 and its outcomes.

Research Design and Methods
We performed a propensity score-matched cohort study with active comparators using a large UK primary care dataset. Adults with type 2 diabetes patients and a current prescription for metformin and other glucose lowering agents (MF+) were compared to those with a current prescription for glucose-lowering agents that did not include metformin (MF-). Outcomes were confirmed COVID-19, suspected/confirmed COVID-19, and associated mortality. A negative control outcome analysis (back pain) was also performed.

There were 29,558 and 10,271 patients in the MF+ and MF- groups respectively who met the inclusion criteria. In the propensity score-matched analysis, the adjusted hazard ratio for suspected/confirmed COVID-19, confirmed COVID-19, and COVID-19 related mortality were 0.85 (95%CI 0.67, 1.08), 0.80 (95%CI 0.49,1.30), and 0.87 (95%CI 0.34, 2.20) respectively. The negative outcome control analysis did not suggest unobserved confounding.

Current prescription of metformin was not associated with the risk of COVID-19 or COVID-19 related mortality. It is safe to continue prescribing metformin to improve glycaemic control in patients with diabetes, despite concerns about an impending second wave of COVID-19.


Original languageEnglish
Article numberdgab067
JournalJournal of Clinical Endocrinology and Metabolism
Early online date9 Feb 2021
Publication statusE-pub ahead of print - 9 Feb 2021


  • Type 2 diabetes mellitus, Metformin, COVID-19, SARS-CoV-2 infection