The use of metformin – the most common initial medication for people with type 2 diabetes – was associated with a lower rate of mortality from COVID-19 among people with diabetes in a study in Alabama, confirming five previous studies.
Do you take metformin? It’s the first-line therapy used to lower glucose levels in people with type 2 diabetes. A recent study found that metformin use was associated with a lower rate of COVID-related death among people with type 2 diabetes. Since people with diabetes are at increased risk for severe illness from COVID-19, including hospitalization and death, the relationship between metformin and COVID outcomes in this report may be of interest to many people around the world who take the medication.
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The study looked at the electronic health data from 25,326 people tested for COVID at Birmingham Hospital in Alabama, including healthcare workers, between February and June of 2020. Of those tested, 604 people were positive for COVID-19 – and 239 of those who were positive had diabetes. These results showed that the odds of testing positive for COVID were significantly higher for people, particularly Black people, with certain pre-existing conditions, including diabetes. This does not mean people with diabetes are more likely to get COVID-19, only that people with diabetes were more likely to test positive at this hospital.
Importantly, the study found an association between metformin use and risk of death – the study reported that people who were on metformin before being diagnosed with COVID-19 had a significantly lower chance of dying:
- People taking metformin had an 11% mortality (or death) rate, compared to 24% for those with type 2 diabetes not on metformin when admitted to the hospital.
- This benefit of metformin remained even when people with type 2 diabetes and kidney disease or chronic heart failure were excluded from the calculations. This is important because people with kidney or heart disease are often advised against taking metformin. By removing this population, it helps to support the notion that metformin may be involved in this difference.
- Body weight and A1C were not associated with mortality among people with diabetes taking metformin. This suggests that the association of metformin use with reduced COVID-related deaths was not due to the effects of the medication on weight or glucose management.
The data suggest that being a person with diabetes who takes metformin may provide some level of protection against severe COVID-19 infection among people with diabetes. Other studies have shown similar results, though it is not known whether metformin may itself reduce COVID-related deaths among people with type 2 diabetes. The authors discussed some previously reported effects of metformin beyond lowering glucose levels, such as reducing high levels of inflammation (the body’s natural way of fighting infection), which has been described as a risk factor in severe COVID infection. Severe infection with COVID-19, resulting in hospital admission, can lead to damage to the kidneys and decreased oxygen supply to the body’s tissues – and in these circumstances, serious side effects of metformin can occur.
“Given that COVID leads to higher mortality rates and more complicated hospital courses in people with diabetes, it is important to consider whether specific diabetes medications can provide some relative degree of protection against poor COVID outcomes,” said Dr. Tim Garvey, an endocrinologist at the University of Alabama at Birmingham. “This study adds to growing evidence that people with type 2 diabetes treated with metformin have better outcomes than those not receiving metformin.”
Dr. Garvey also cautioned: “Of course, these case-control studies show associations and do not rise to the level of evidence that might be found by a randomized clinical trial. For example, people with diabetes not treated with the first-line drug, metformin, may have a larger number of diabetes complications or longer duration of disease compared with people not on metformin – which could explain the more severe outcomes. In any event, we advocate for early administration of COVID-19 vaccines and other protective measures for people with diabetes.”
Professor Philip Home, a professor of diabetes medicine at Newcastle University in the UK, agreed, saying, “Multiple studies have now addressed the issue of whether metformin and insulin use are associated with better or worse outcomes in people with diabetes who contract COVID-19. In line with previous literature on other diseases, it was expected that people on metformin would do better, and people on insulin worse, than people with diabetes not using these medications. This is confirmed.”
Home continued: “It is believed to happen because people using metformin are younger and have better kidney function than those not taking the medication, while those on insulin tend to have other medical conditions. The good news is that if you have type 2 diabetes and are taking metformin, you are likely to be fitter than if you have type 2 diabetes and do not take the medication – but there is no evidence that metformin itself will make a difference to your outcome if you do get COVID-19. So, get vaccinated as soon as possible!”
To learn more about metformin, read “Everything You Always Wanted to Know About Metformin, But Were Afraid to Ask.”