Early treatment with the diabetes drug metformin reduced the risk of long COVID by almost half in a study of more than 1,100 adults. Researchers at the University of Minnesota followed the participants for 10 months. Data from the Centers for Disease Control and Prevention concludes that approximately 11% of the population suffers from long COVID, and the new research suggests that half of these cases could be prevented by taking an inexpensive drug.

“Long COVID is a significant public health emergency that may have lasting health, mental health and economic sequelae, especially in socioeconomically marginalized groups, and metformin is safe, low-cost, and widely available,” the study authors wrote in a preprint for The Lancet.

According to MedPage Today, Dr. Carolyn Bramante and her colleagues also tested the antiparasitic drug ivermectin and the antidepressant fluvoxamine, but found no reduction in long COVID with either drug versus a placebo. Bramante said that metformin was particularly effective in protecting people who were overweight or had obesity. She added that metformin inhibits SARS-CoV-2, the virus that causes COVID-19, and has been shown to improve T-cell immunity. For the study, metformin was started within four days of the onset of symptoms.

In addition to decreasing the risk of developing long COVID by 42%, the study found that it prevented 40% of emergency room visits, hospitalizations, and deaths. Although the study subjects were overweight, the authors said their findings could likely be translated to people with normal BMI.

“The study also confirms earlier research that shows decreased risk of hospitalization or death from COVID-19 in people taking metformin,” said Dr. Jacob Teitelbaum, a board-certified internist, and author of From Fatigued to Fantastic.

While some studies began with a metformin dosage of 1500 milligrams (mg) a day, this level was sometimes associated with nausea or diarrhea. In the current study, the metformin was slowly increased over six days: 500 mg on day one; 500 mg twice daily for four days; then 500 mg morning and 1,000 mg evenings through 14 days.

Teitelbaum suggests that long COVID represents an energy crisis in the body and taking metformin can increase energy production by improving insulin sensitivity in those who are overweight.

“In summary, this new study found that 10.6% of people who got placebo developed long COVID, but only 6.3% got long COVID among patients who were taking metformin — effectively preventing 42% of cases of long COVID,” said Teitelbaum, who is an expert in treating chronic fatigue syndrome and fibromyalgia. “Not only is long COVID treatable, but with $10 worth of metformin taken early in the infection, we could have prevented 5 million cases of long COVID in the U.S.”