Birmingham, UK—Despite earlier research suggesting that metformin prescribed to treat type 2 diabetes might confer some level of protection against severe COVID-19, a recent study finds that the most commonly prescribed glucose-lowering agent has no influence on either susceptibility to or outcomes from infection with novel coronavirus.

The report in The Journal of Clinical Endocrinology & Metabolism provides some valuable advice, however, on how diabetes patients can stay safe while recovering from COVID-19.

Researchers from the University of Birmingham and colleagues 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-).

Defined as the outcomes were confirmed COVID-19, suspected/confirmed COVID-19, and associated mortality. The study team also performed a negative-control outcome analysis on back pain.

Meeting the inclusion criteria were 29,558 and 10,271 patients in the MF+ and MF- groups, respectively. Researchers report that, 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.

“Current prescription of metformin was not associated with the risk of COVID-19 or COVID-19 related mortality,” the authors conclude, adding that continued prescribing of metformin for glycemic control is safe.

“Type 2 diabetes has been identified as a predictor of severe COVID-19 and mortality. However, little is currently known about which specific glucose-lowering agents can be used to safely maintain or improve glycemic control amid the COVID-19 pandemic,” the researchers note. “In our primary care-based study, we found that patients with type 2 diabetes who received a prescription of metformin (plus other glucose-lowering agents) within 90 days of the study start period were not more likely to present to primary care with confirmed or suspected COVID-19 related disease compared with those not taking metformin. There was no significant increase in COVID-19 related mortality or all-cause mortality.”

The authors point out that their findings are important because a majority of patients with type 2 diabetes are prescribed metformin and that, for many patients, metformin is critical for maintaining glycemic control and managing weight. It also has a long-established efficacy and safety track record, they add.

They caution, however, about risk of adverse effects in COVID-19 patients because of its side-effect profile. “Adherence to usual guidance on sick-day rules, however, remains strongly advised if the patient is at risk of dehydration,” the authors emphasize, advising healthcare professionals to caution patients taking metformin who develop symptoms consistent with COVID-19 or other infections. In some cases, based on consultation with the prescriber, the medication might need to be withheld if there are concerns about acidosis. Patients also should consider increased monitoring of blood glucose during the illness, the article notes.

Overall, the study concludes that metformin has little effect on COVID-19 susceptibility or severity, adding, “This is reassuring given that patients with diabetes are more susceptible to mortality with COVID19, and that metformin is the most commonly prescribed glucose-lowering medication. Optimizing glycemic control should continue to be the best advice for patients with diabetes, especially if rates of COVID-19 rise.

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