This content originally appeared on Everyday Health. Republished with permission.

By Lisa Rapaport

Key Takeaways

In people with COVID-19, metformin reduced coronavirus levels in the body 4 times more than a placebo pill.
There’s evidence that metformin might make COVID-19 less contagious.
Because research is limited, doctors do not yet recommend that people with COVID-19 begin taking metformin.

Metformin, a decades-old generic drug for type 2 diabetes, may also help treat COVID-19, a new study suggests.

Scientists at the University of Minnesota randomly assigned more than 1,300 adults with COVID-19 to take metformin or a placebo pill. All of the participants took nasal swab tests for viral levels after 1, 5, and 10 days.

Lab tests showed that metformin significantly reduced the amount of COVID-19 virus circulating in the body and also decreased the odds that virus levels would rebound after an initial reduction during treatment, according to study results published in Clinical Infectious Diseases.[1]

Among the key research results:

On average, metformin reduced the amount of virus in the body almost 4 times more than the placebo pill.
People taking metformin were 28 percent more likely to have undetectable levels of the virus in their body at either day 5 or day 10 of the study.
Participants on metformin were 32 percent less likely to experience what’s known as rebound — when levels of the virus initially decrease but then become higher again.

“The results of the study are important because COVID-19 continues to cause illness, both during acute infection and for months after infection,” says lead study author Carolyn Bramante, MD, an assistant professor of medicine at the University of Minnesota.

How Metformin Might Fight COVID-19

The metformin study wasn’t designed to figure out why or how this diabetes treatment might tamp down the coronavirus. But the drug blocks activity of a protein known as mTOR, Dr. Bramante says. This protein plays a role in cell growth and reproduction and impacts immune responses.

“We hypothesized that metformin’s inhibition of mTOR may cause a reduction in SARS-CoV-2,” the specific type of coronavirus that causes COVID-19, Bramante says.

However, the possible benefits of metformin as a COVID-19 treatment aren’t yet clear, with previous studies yielding conflicting results.

One study of metformin in COVID-19 patients found that the drug didn’t significantly reduce their odds of being hospitalized with severe infections, according to the National Institutes of Health (NIH). But the NIH notes that another study found COVID-19 patients who took metformin were 42 percent less likely to be hospitalized with severe infections or die.[2]

Metformin May Make COVID-19 Less Contagious

Still, the results of the new study are particularly promising because reducing levels of the virus circulating in the body also decreases so-called viral shedding, or releasing copies of the virus from the body that can infect others, says Mark Siedner, MD, MPH, co-author of an editorial accompanying the study and an associate professor of medicine at Harvard Medical School and Massachusetts General Hospital in Boston.[3]

“The shorter duration of viral shedding, the shorter the duration of potential contagiousness and transmission risk,” Dr. Siedner says.

Should You Start Taking Metformin for COVID-19?

Even though metformin has potential as an intervention against COVID-19, it’s not yet recommended for this use. There still isn’t enough evidence to prescribe metformin for people with milder COVID-19 infections, and the NIH recommends against using this drug in patients hospitalized with severe infections unless they’re part of a clinical trial.[4]

“Based on the data we have now, I would not personally prescribe metformin for treatment of COVID-19, nor would I recommend its use,” Siedner says.

Editorial Sources and Fact-Checking