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Experts say people being diagnosed with diabetes while being treated for COVID-19 may simply have had undiagnosed cases of the disease. Getty Images
  • A letter in the New England Journal of Medicine suggests the possibility that COVID-19 could be causing the onset of type 1 and type 2 diabetes in some people.
  • However, experts tell Healthline that many of these people could have had prediabetes or undiagnosed cases of diabetes before entering the hospital.
  • The experts recommend that medical professionals track these newly diagnosed diabetes cases to see how they progress after recovering from COVID-19.

Is COVID-19 causing the onset of type 1 or type 2 diabetes?

A recent letter published in the New England Journal of Medicine highlights observational findings that raise this connection as a possibility.

“There is a bidirectional relationship between COVID-19 and diabetes. On the one hand, diabetes is associated with an increased risk of severe COVID-19. On the other hand, new-onset diabetes and severe metabolic complications of preexisting diabetes, including diabetic ketoacidosis and hyperosmolarity for which exceptionally high doses of insulin are warranted, have been observed in patients with COVID-19,” doctors from around the world wrote in the letter.

The relationships between COVID-19 and type 1, type 2, and prediabetes have created challenges in treating and caring for patients as well as increasing their risk of complications and fatality.

Experts, however, caution against simplifying this letter to mean that COVID-19 is actually causing type 1 and type 2 diabetes.

“There are several viruses that have been implicated directly with the full onset of type 1 diabetes,” explains Dr. David Nathan, the director of the Diabetes Center and the center of clinical research at Massachusetts General Hospital in Boston.

“There’s a seasonality to type 1 diabetes. The everyday flu is most commonly associated with the onset of type 1 diabetes, but research has shown the disease was developing long before the symptoms develop,” Nathan told Healthline.

Nathan is referring to the process of the immune system starting to attack and destroy beta-cells responsible for producing insulin. This autoimmune attack results in autoantibodies — evidence of the body attacking itself.

TrialNet, for example, has determined through decades of research that autoantibodies in people with type 1 diabetes often develop years prior to the full onset of the disease.

Nathan said the stress of a virus such as the flu or COVID-19 is simply the final catalyst that creates enough stress that insulin production finally declines severely enough to result in diabetic-related ketones and thus the common symptoms of type 1 diabetes.

“It’s associated with the onset, but it’s not the cause,” said Nathan. “That’s a critical detail to understand.”

Nathan said it can be difficult to determine the connection between COVID-19 and type 2 diabetes because of how the overall health and records of patients being treated for COVID-19 are being tracked and managed.

“The stress associated with COVID-19 is pretty profound and people are pretty damn sick by the time they’re being hospitalized,” said Nathan. “And then many are intubated, which means they also end up on tubed-feeding.”

This physical trauma to the body could easily lead to stress-induced hyperglycemia (high blood sugar).

For some, that should theoretically correct itself if and when they recover from COVID-19, but others may be one of the more than 7.3 million people in the United States with undiagnosed diabetes.

COVID-19 cannot only create a stressful environment capable of elevating blood sugar levels, but it can also bring people into the hospital where their blood sugar levels are measured.

People with undiagnosed prediabetes or undiagnosed type 2 diabetes who come into the hospital for anything from a urinary tract infection to a heart attack are likely to receive a diabetes diagnosis, too.

With many of Massachusetts General Hospital’s 1,100 beds being used by people with COVID-19, Nathan said it isn’t surprising that more cases of type 2 diabetes are being identified and diagnosed.

“Does COVID-19 really cause high blood sugars or were their blood sugars high beforehand and it was simply finally diagnosed?” asked Nathan. “One way to determine this would be to look at their HbA1c levels at the time of diagnosis.”

HbA1c (or A1C, for short) essentially measures the amount of glucose attached to your red blood cells. The results of this blood test account for blood sugar levels from the prior 3 months because of how the body renews red blood cells.

This means if a person’s A1C level was above 6 or 7 percent, they likely had been in the process of developing type 2 diabetes prior to developing COVID-19.

Nathan suggested that blood sugar levels could potentially return to normal once people without diabetes or prediabetes had recovered from the virus.

Nathan said information on post-treatment for these people isn’t being collected or tracked.

“How many people have diabetes when they enter the door? How many continue to have diabetes after they’ve recovered from COVID? Are they testing for markers of autoimmunity or elevated C-peptide levels to indicate type 1 versus type 2 diabetes? These are the things we’d need to standardize and track, much like the work of TrialNet,” he said.

In the United States, this type of health registry and tracking doesn’t exist in a mandatory, efficient method. In other regions, such as Scandinavia — which has the highest number of type 1 diabetes cases around the globe — there’s a registry for every type 1 diabetes diagnosis.

This helps research toward improved treatments and cures.

“It needs to be standardized across different countries, but if they’re just going to collect basic information, it isn’t going to be very useful,” said Nathan.

Dr. Zachary Bloomgarden, a professor at Mount Sinai Hospital in New York City specializing in endocrine and diabetes care, echoed the same concerns.

“Any viral infection can worsen type 1 or type 2 diabetes, but we also don’t know the association of blood sugar management and COVID severity,” Bloomgarden told Healthline.

“What is the HbA1c in people with diabetes who develop COVID-19 and how does that correlate with the outcome? You’d think we could answer that question by now, but we don’t have that information,” he said. “A lot of people who have diabetes and develop COVID-19 have pretty poorly controlled diabetes with an A1C over 9 percent, but no one is tracking this aspect of who recovers and who doesn’t.”

There is a registry in the United States that’s starting to collect information on people with type 1 diabetes.

Bloomgarden added that there’s no reason to think people with diabetes are more likely to contract the virus, but their ability to survive and recover is concerning.

“This issue of severity is a worrisome aspect of it. We have to add it to the risk factors but virtually the same increase in risk has been shown for those with high blood pressure and people with heart disease, lung disease, and many other comorbidities,” he said.

“They’re not even tracking diabetes separately in its own category but simply as one of the many comorbidities. And there is no organized ‘they’ in the first place,” Bloomgarden said. “The reality is that we need data, a good amount of data, and it isn’t being collected.”

Ginger Vieira has lived with type 1 diabetes and celiac disease since 1999 and fibromyalgia since 2014. She’s the author of four books: “Pregnancy with Type 1 Diabetes,” “Dealing with Diabetes Burnout,” “Emotional Eating with Diabetes,” and “Your Diabetes Science Experiment.” Ginger creates content regularly for Diabetes Strong, Diathrive, YouTube, and Instagram. Her background includes a bachelor of science degree in professional writing and certifications in coaching, personal training, and yoga.