Some data suggest that metformin may help treat infection and reduce long COVID risk. But so far these data are not conclusive and we need further studies before metformin would be recommended for treating COVID.
Metformin is an FDA approved drug with a good safety history. It is most often used to help lower blood sugar in those with type 2 diabetes or to prevent onset of type 2 in those pre-diabetic. Early in the pandemic some researchers noticed that patients already on metformin appeared to have better outcomes during a COVID-19 infection. Since then studies have looked to see if metformin may treat active infections and reduce the risk of long COVID.
Metformin to treat COVID-19
One study found no benefit in the use of metformin on preventing emergency room visits or hospitalizations. A second study also showed no decrease in hospitalization, death, or low oxygen in the blood. However, further analysis showed that metformin *DID* reduce the number of emergency room visits and death when these outcomes were evaluated separately. A third study found that those who took metformin had significantly less virus in their nasal samples than those who did not take metformin. These patients also had improved outcomes such as reduced severity of infection. These studies were similar to findings from another study. Finally, a review of the combined data from these studies also confirmed that there may be a benefit, but more trials are needed.
These data suggest that there are possible benefits, but not all studies agreed. Except for the one review, all of the other studies included randomized control trials where patients were randomly assigned to receive a placebo or metformin. Some of the trials used different dosages of metformin and started and ended its use at different points after someone tested positive. This could be why differences were seen in some of the studies and this is why more data is needed.
Metformin to prevent long COVID
The potential harms of a COVID-19 infection include more than just hospitalization and death. It is estimated that 2-20% of individuals may develop long COVID, also called post-acute sequelae of COVID-19. While some patients with long COVID recover, some do not and suffer from various serious symptoms that change their life. This is why finding ways to lower the risk of long COVID is so important.
Two randomized studies have shown a reduced rate of long COVID in those who took metformin compared to patients who took a placebo. However, one of the studies showed the most benefit if a patient was unvaccinated.
Other limitations
Another important limitation is that many of these studies only included people ages 30-85 who were overweight or obese or had other known risk factors for severe COVID infections. More data and trials are needed to see if the benefits apply to those outside of these categories.
Metformin is not officially recommended outside of clinical trials for those infected with COVID-19. The good news is, if you’re already on metformin for another reason it is possible that you may benefit from this effect. Other patients may still discuss it as an option with their medical provider given their specific situation. Since it is FDA approved for other uses some providers may prescribe it for other things, a process known as off-label use. Hopefully we will have more data that will inform future guidance soon and help us determine if it should become a standard treatment.
