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High Blood Sugar Can Increase COVID-19 Risk, Even Without Diabetes

Woman checking her blood sugar levels.

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Key Takeaways

  • Having high blood sugar while in the hospital with COVID-19 can significantly increase a person’s chance of severe illness.
  • Healthcare professionals should screen for, monitor, and treat patients admitted with hyperglycemia.

A recent study out of Spain shows that COVID-19 patients admitted to the hospital with high blood glucose (sugar) independent of diabetes have an increased risk of mechanical ventilation use, ICU placement, and death.

Researchers examined more than 11,000 patient records pulled from the SEMI-COVID-19 Spanish Registry. These records detailed patients admitted to the hospital with COVID-19 from March 1 to May 30, 2020. After analyzing the data, researchers determined that patients with abnormally high blood glucose levels, also called hyperglycemia, were more than twice as likely to die from the virus as patients with normal blood glucose levels. This November study was published in Annals of Medicine. 

High blood sugar levels are generally characterized as a blood glucose reading above 180 mg/dL.

“This study is similar to what we were seeing before COVID-19 in regards to hyperglycemia contributing to poor outcomes,” Cecilia C. Low Wang, MD, FACP, professor of medicine in the division of endocrinology, metabolism, and diabetes, at the University Of Colorado Anschutz Medical Campus School Of Medicine, tells Verywell. “But the big question now is whether COVID-19 is causing hyperglycemia. This virus brings all sorts of complications.”

What This Means For You

Maintaining a normal weight, staying active, and eating a balanced diet is critical to not only avoid Type 2 diabetes but to decrease risk factors that can contribute to poor health outcomes related to illness, especially COVID-19.

Proactive Monitoring in the Hospital Decreases Risk

The study emphasizes the importance of screening blood glucose numbers upon hospital admission, and continuously monitoring and treating those with hyperglycemia to help decrease their chances of becoming critically ill.

“Baseline labs, including blood glucose, are taken from almost everyone upon admission to the hospital,” Low Wang says. “However, high blood glucose numbers are often overlooked and not used to make medical decisions.” 

She recommends that COVID-19 patients admitted to the hospital with high blood sugar be flagged and monitored throughout their hospital stay. She says patients should also be treated with insulin as needed to help stabilize their glucose numbers and decrease their chances of severe illness, and subsequent death, from the progression of COVID-19, or any illness.

Causes of Hyperglycemia

Hyperglycemia is a common development for people in the hospital, especially when they are critically ill and in the ICU. Research has shown that tight control of blood glucose numbers is crucial. If left untreated, hyperglycemia can result in a 31% increased mortality rate.

The Hormone Health Network explains that many conditions can cause or worsen hyperglycemia, even for those who do not have a history of diabetes. These common causes include:

  • Physical stress of illness, trauma, or surgery
  • Decrease in physical activity
  • Steroids like prednisone and some other medicines
  • Liquid food given through a feeding tube or nutrition given intravenously
  • Certain medical conditions such as Cushing disease or syndrome

The use of dexamethasone—a corticosteroid that can cause hyperglycemia—has been highlighted in the media as a possible COVID-19 therapy drug that has shown to decrease mortality in some critically ill patients. Although this treatment has been a positive outcome for many people, a trial out of the U.K. found that its use can cause unwarranted and dangerous hyperglycemic levels in those with diabetes, pre-diabetes, and even expose undiagnosed diabetes. As a result, the Joint British Diabetes Societies (JBDS) published guidelines on how to treat COVID-19 patients with and without diabetes receiving steroid therapy.

Why High Blood Sugar Is Dangerous

The effects of untreated hyperglycemia can wreak havoc on the body, especially for those who are critically ill. If blood glucose numbers are not tightly managed in the hospital, the Hormone Health Network says the following problems may occur:


  • Longer hospital stay
  • Slower wound healing
  • More infections
  • More disability after discharge from the hospital
  • Higher risk of death
  • Increased risk for getting readmitted to the hospital

How to Prevent Hyperglycemia and Type 2 Diabetes

Type 2 diabetes is a condition that can be prevented and reversed with the implementation of daily life style changes, and in the midst of a pandemic, it is important to keep your body healthy and active to decrease the chances of severe illness if you do contract COVID-19.

“Everyone is at risk of getting COVID-19,” Mary de Groot, PhD, associate professor of medicine and acting director of the Diabetes Translational Research Center at Indiana University, tells Verywell. “If you are diabetic, or pre-diabetic, you need to take all the steps to manage your blood sugar. Work with your provider to keep your numbers as normal as possible, eat healthy, and exercise. It is important to decrease your risk of exposure to COVID-19.”

Losing a small amount of weight is one of the ways to prevent Type 2 diabetes. De Groot explains that dropping just 5-7% of your weight can help keep diabetes a bay. The Centers for Disease Control and Prevention (CDC) also provides a practical guide to help you decrease your chances of developing Type 2 diabetes.

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Article Sources
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  3. Hormone Health Network. Hypoglycemia in the Hospital. Updated May 2019.

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