Metformin, a medication typically used as a treatment for Type 2 diabetes, has shown promise as an effective treatment for long COVID, according to a study by University of Minnesota researchers published Thursday in The Lancet. But researchers caution that more study is needed before the drug can be prescribed as a treatment for people who currently have the illness.

Long COVID, sometimes called long-haul COVID or post-COVID conditions, may have a number of different symptoms, and can last weeks, months or even years.

Symptoms range from fatigue to brain fog to heart palpitations, according to the Centers for Disease Control and Prevention, as well as potentially hundreds of other symptoms that can be difficult to explain or manage. It’s unclear who exactly will get long COVID, but the chronic illness can affect up to 10 percent of people who’ve had the virus, according to the release.

The study, which was conducted as part of the COVID-OUT project, was investigating if early treatment with metformin, ivermectin or fluvoxamine could prevent severe COVID and long COVID.

In placebo-controlled tests it found that people who received metformin were over 40 percent less likely to develop long COVID, compared to those who received a placebo. And for participants who began taking the medication within the first few days of being symptomatic, it decreased the risk of long COVID by 63 percent.

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

While this research is notable, Bramante cautions that people who currently have long COVID shouldn’t take metformin as a potential treatment.

“While it is a very safe medication with few contraindications, I think we wouldn’t want people to just take any therapy without knowing whether or not it works,” she said. “So a trial assessing whether or not metformin treats long COVID is one important next step in this body of literature.”

The study was conducted remotely, during the height of the pandemic, to limit the spread of the virus and conserve personal protective equipment, Bramante said. Once someone consented and began the study, medications were shipped overnight to their homes.

She says one of the challenges during this process was that the science around COVID was developing in real time.

“The electronic health record code for long COVID didn’t even exist until October 2021,” Bramante said. “And even since then, the definitions of long COVID have continued to change. But one of the strengths of our means of assessing long COVID is that we know a medical provider assessed for other causes of what might be affecting participants, and ruled out that it was something else other than long-term sequelae of COVID.”

The World Health Organization defines long COVID as “the continuation or development of new symptoms three months after the initial SARS-CoV-2 infection, with these symptoms lasting for at least two months with no other explanation.”

According to the release, metformin was predicted to be effective against the virus by a simulator, developed by faculty at the U of M School of Medicine and the university’s  biomedical engineering department.

Bramante said the model showed that “metformin stops a protein that the virus uses to replicate itself.”

Ivermectin and fluvoxamine did not prevent long COVID, according to the release.