Researchers looked back in time and analyzed claims data from people in United Health Group’s database who had filled prescriptions for metformin over the past year and had been hospitalized because of a confirmed COVID-19 case. Of the 6,256 people who met those criteria, 3,302 (53%) were women. When the researchers looked deeper at the data, they found that women with type 2 diabetes or obesity who had filled a 90-day metformin prescription before hospitalization had a 21% to 24% reduced likelihood of mortality, compared to similar women not taking the medication. The beneficial effect was not found in men.
“We knew that metformin had anti-inflammatory effects in the body; that was well documented before COVID-19," Carolyn Bramante, MD, lead study author and assistant professor of medicine at the University of Minnesota Medical School in Minneapolis, tells Verywell. “We also knew that metformin reduces inflammatory proteins more in females than males; that has been documented in both human and animal studies. But [earlier this year] when computer modeling showed that metformin might be effective against the virus directly, we had a new hypothesis.”
The study proved the hypothesis: there is a connection between metformin and a reduced risk of dying from COVID-19.
Metformin Decreases Blood Sugar and Inflammation
Metformin is an oral medication that reduces the amount of sugar—also referred to as glucose—in your blood. It works by decreasing the amount of glucose your liver releases into your bloodstream and by enhancing your body’s response to the insulin your pancreas secretes. It is often used to treat type 2 diabetes, a condition caused by high blood sugar. When blood sugar is too high (more than 180 mg/dL), inflammation can be triggered.
This type of inflammation is not necessarily swelling you can see, such as in an injured knee. Instead, it happens internally, such as in the walls lining the blood vessels. That kind of inflammation is dangerous. If the blood vessel walls become inflamed, the area through which blood flows becomes smaller. Narrowed blood vessels mean increased blood pressure, which over time can damage the inside of the blood vessel and possibly result in a blood clot that breaks off, travels to the brain, and causes a stroke.
If inflammation occurs in the lungs, airways become constricted. This is why people who have type 2 diabetes are at high risk for heart or lung disease. And it is also the type of inflammation that causes severe complications in people who have COVID-19.
A study recently published in the Annals of Medicine found that high blood sugar can increase the risks that come with COVID-19—such as being put on a mechanical ventilator or dying—whether you have diabetes or not. Metformin not only reduces blood sugar levels, but also the inflammation associated with chronic conditions.
Obesity is the a significant risk factor for COVID-19, and men have a higher risk of developing severe cases. Men tend to have more fat around their organs, and those fat cells secrete many of the molecules associated with inflammation and severe cases of COVID-19: tumor necrosis factor-a (TNF-a), interleukin-6 (IL-6), and D-dimer. TNF-a contributes to insulin resistance and is higher in people with type 2 diabetes and obesity. Metformin, however, decreases the level of TNF-a, and has been shown to do so slightly more in females than males.
“The benefit may not be as large in men, but that doesn’t mean that men won’t see any effect,” Bramante says. “Women may just have a better anti-inflammatory effect.”
What’s Next?
Now researchers need to go a step further. When people on metformin are hospitalized, their medication is stopped, so the results of the study were from people who were not taking metformin while they were being treated in the hospital for COVID-19. “Any long-acting diabetes medication is stopped in the hospital because [healthcare providers] want to control blood sugar for patients,” Bramante says.
Future studies could evaluate the use of metformin for people with COVID-19 who are hospitalized, but first researchers would do an outpatient study to evaluate the use of metformin in people with COVID-19 who are not hospitalized or its potential use as a preventive therapy. “We need to do formal studies, including an outpatient trial to see if metformin does produce clinically meaningful results,” Bramante says.
If metformin becomes a way to prevent or treat COVID-19, getting it to the public would be easy, Bramante says. “It’s quite safe and widely available, it’s a tablet, it doesn’t have to be refrigerated, and it is inexpensive," she says. “As a total package, metformin is very compelling.”
So if you are a woman taking metformin, you may take some comfort in knowing that your medication may help protect you if you were to contract COVID-19. But whether you already take metformin or not, you should do all you can to avoid getting the virus, including:
Wash your hands frequentlyUse hand sanitizer when soap and water are not availableWear a mask when you are outside of your own homeKeep your distance from other people when out in publicChoose healthy foods and drinks over processed, sugary optionsMove your body for 30 minutes most days of the weekMake sleep a priority
“The fact remains that we need a multi-pronged approach against COVID-19 to save lives immediately, such as keeping distance and wearing masks, and then longer-term approaches, such as the vaccine,” Bramante says. “Either way, we’ll need outpatient treatment options like metformin for people who do get the virus.”
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.
