Can COVID-19 Cause Diabetes?

As the pandemic wears on, researchers are discovering more about the link between COVID-19 and diabetes. While it's been known for some time that those with diabetes are more likely to experience severe outcomes from the virus, there is now emerging evidence suggesting a two-way relationship between diabetes and COVID-19.

That is, not only is diabetes associated with an increased risk of worse outcomes with COVID-19, but the virus itself may trigger diabetes in people who haven't previously been diagnosed with the disease.

Doctors saw the first signs of this possible link several months ago, when they noticed something unusual in a small number of hospitalized adult COVID-19 patients: They had elevated blood sugar and high levels of chemicals known as ketones (which the body uses as an alternative source of fuel when it lacks enough insulin to break down sugar). Both factors suggested diabetes. But these patients didn't seem to have classic type 2, nor did they have the markers of type 1. Was it new-onset diabetes? A new form of the disease? Or something else altogether?

Doctors are still looking for answers, but they believe that one possible explanation is that the stress of being hospitalized with COVID-19 may be uncovering a risk for diabetes or the presence of undiagnosed diabetes.

When somebody with COVID-19 is admitted to the hospital, “there are lots of hormones that make glucose go up,” explains Robert Eckel, M.D., professor of medicine emeritus in the division of endocrinology, metabolism and diabetes at University of Colorado Anschutz Medical Campus in Aurora, Colo. “This may be the tipping point for many people who are running around at high risk for diabetes, or have diabetes and don't know it.”

In a letter published in the New England Journal of Medicine, in August, 17 medical experts floated another possibility: Could it be that COVID-19 is the trigger? As they noted in their letter, some of the organs involved in controlling blood sugar are rich in a receptor called ACE2 — one COVID-19 is known to use to infect cells. As it does so, the virus may destroy the body's insulin-producing cells, essentially bringing on what may be its own kind of diabetes.

"There have been a number of cases that look like there was no risk for diabetes — no family history, no phenotype of type 2 or type 1 diabetes, no antibodies and other antigens that are typical of type 1,” Eckel says. “So this looks like it may be a unique form of diabetes."

But experts say more research is needed. To that end, Eckel and 16 other diabetes researchers from around the world are working together “to understand if this is a unique type of diabetes or if, in fact, it's the super-imposition of a stress condition such as hospitalization for COVID-19” causing the mysterious new diagnosis of diabetes.