A team of researchers from the University of Minnesota has discovered that metformin, a widely prescribed medication for diabetes management, can effectively inhibit the onset of long COVID, according to a new study published in The Lancet Infectious Diseases.

The study found a 41% reduction in long COVID rates among people who used metformin at the time of COVID infection and saw a 42% reduction in emergency room visits, hospitalizations, or death among COVID-19 patients who started metformin treatment.

In the COVID-OUT study, researchers from multiple academic institutions tested the effectiveness of three generic medications—metformin, ivermectin, and fluvoxamine—in adults who had been diagnosed with COVID-19 within the last three days. 

According to researchers, the randomized, quadruple-blinded, placebo-controlled clinical trial was the first in the country to study whether these medications could prevent severe outcomes and long COVID. The trial found that people who took metformin within seven days after the onset of COVID symptoms were 41% less likely to experience long COVID than those who had placebo—with a 63% reduction if metformin was started within four days.

“The results of this study are important because long COVID can have a significant impact on people’s lives,” says Carolyn Bramante, MD, principal investigator and an assistant professor at the University of Minnesota Medical School, in a release. “Metformin is an inexpensive, safe, and widely available drug, and its use as a preventive measure could have significant public health implications.”

Previous data suggested that metformin’s anti-inflammatory and anti-infectious properties could treat COVID-19 infection. The antiviral effect was confirmed in a recent analysis of the viral load of COVID-OUT study participants, which is currently available as a preprint. Researchers reported a 3.6-fold decrease in the SARS-CoV-2 virus level in people who received metformin instead of placebo.

“We hope the US and other nations update their guidelines to include metformin as a treatment option for people with COVID-19,” says Elaine Lissner, founder and trustee of the Parsemus Foundation, a research funder part of the nonprofit coalition funding the trial, in a release. “This would be the first universally available treatment, giving more people a tool to combat the disproportionate impact of this disease.”