COVID and Diabetes

Research explores whether diabetes in COVID-19 patients is new or merely previously undiagnosed

Image of COVID blood test vials with a box nearby that says 'Diabetes'
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This article is part of Harvard Medical School’s continuing coverage of COVID-19.

Many COVID-19 patients newly diagnosed with diabetes during hospital admission may have a temporary form of the disease related to the acute stress of the viral infection, and their blood sugar levels may return to normal soon after discharge, a study by Harvard Medical School researchers at Massachusetts General Hospital found.

These patients are more likely to be younger, nonwhite, and uninsured or on Medicaid compared with individuals with previously diagnosed diabetes, suggesting many of these new-onset cases may simply be preexisting but undiagnosed diabetes in individuals with limited access to health care services, according to the study published in the Journal of Diabetes and Its Complications.

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High rates of newly diagnosed diabetes mellitus have been reported in COVID-19 hospital admissions around the world. It is still unclear, however, if this phenomenon represents truly new diabetes or previously undiagnosed cases.

It is also not known what the cause of these elevated blood sugars may be, and whether patients’ blood sugars improve after resolution of COVID-19 infection.

Preexisting diabetes in people with COVID-19 has been associated with higher rates of hospitalization, intensive care unit admission, mechanical ventilation, and death.

“We believe that the inflammatory stress caused by COVID-19 may be a leading contributor to new-onset or newly diagnosed diabetes,” said lead author Sara Cromer, HMS instructor in medicine and an investigator with the Department of Medicine–Endocrinology, Diabetes, and Metabolism at Mass General.

“Instead of directly causing diabetes, COVID-19 may push patients with preexisting but undiagnosed diabetes to see a physician for the first time, where their blood sugar disorder can be clinically diagnosed. Our study showed these individuals had higher inflammatory markers and more frequently required admission to hospital ICUs than COVID-19 patients with preexisting diabetes,” Cromer said.

For its study, the team of investigators looked at 594 individuals who exhibited signs of diabetes mellitus when admitted to Mass General at the height of the pandemic during the spring of 2020. Of that group, 78 had no known diagnosis of diabetes prior to admission.

Researchers learned that many of these newly diagnosed patients—versus those with preexisting diabetes—had less severe blood sugar levels but more severe COVID-19.

Follow-up with these participants after hospital discharge revealed that roughly half the individuals reverted to normal blood sugar levels, and that only eight percent required insulin after one year.

“This suggests to us that newly diagnosed diabetes may be a transitory condition related to the acute stress of COVID-19 infection,” explained Cromer.

Indeed, this key finding supports the clinical argument that newly diagnosed diabetes is likely caused by insulin resistance—the inability of cells to properly absorb blood sugar in response to insulin, resulting in higher-than-normal build-up of glucose in the blood—rather than by insulin deficiency, which is caused by direct and permanent injury to the beta cells which manufacture insulin.

“Our results suggest that acute insulin resistance is the major mechanism underlying newly diagnosed diabetes in most patients with COVID-19, and that insulin deficiency, if it occurs at all, is generally not permanent,” said Cromer.

“These patients may only need insulin or other medications for a short time, and it’s therefore critical that physicians closely follow them to see if and when their conditions improve.”

Adapted from a Mass General news release.