Why COVID is riskier for people with diabetes

When the COVID pandemic began, it quickly became clear that certain groups of people are at particularly high risk for developing worse cases and dangerous complications from the infection. One of the key risk factors for severe COVID: diabetes.

But why?

COVID is considered a respiratory infection. So, how does a virus that enters the body by invading cells in the nose and throat, affect the kidneys—or worsen a metabolic condition, like diabetes?

Over the past few years, researchers have uncovered several possible explanations.

Tough-to-manage blood sugar swings

Generally, viral infections can increase inflammation in people with diabetes and lead to blood sugar spikes that are more difficult to control.

"With any infection, diabetes control can suffer," says Robert Eckel, MD, former president of medicine and science for the American Diabetes Association, and professor emeritus at the University of Colorado School of Medicine, Anschutz Medical Campus in Aurora, Colorado.

There are a few reasons why this is concerning. High blood sugars can interfere with the immune system’s ability to fight infection. It’s possible that they could even create an environment that would enable the virus to thrive.

“If people with diabetes have uncontrolled glucose, they are at higher risk for complications from a viral infection,” says Karl Nadolsky, DO, spokesperson for the American Association of Clinical Endocrinologists (AACE), state chair of the AACE Obesity & Nutrition Disease State Network, and clinical endocrinologist at Spectrum Health in Grand Rapids, Michigan.

Out-of-control production of cytokines

Over time, consistently having higher than normal blood sugar levels can interfere with the response of your immune system—specifically white blood cells that help fight infections, Dr. Nadolsky explains.

A 2018 paper published in the Journal of Diabetes Research suggests that diabetes or obesity were not only associated with the improper functioning of white blood cells, but also greater production of inflammatory molecules called cytokines.

Normally, cytokines help coordinate the body’s response to infection. But in some cases, this response can range out of control, doing more harm than good. This so-called cytokine storm can damage the blood vessels and organs and lead to blood clots, which may help explain why some people with COVID develop more serious complications.

A September 2021 study published in PNAS focuses on one enzyme that may help explain why those with diabetes may be at higher risk for the cytokine storm. Using a mouse model, the researchers pinpointed an enzyme known as SETDB2, which helps regulate inflammatory cytokines. They found that expression of this enzyme is lower among COVID patients with diabetes. They theorized that treating these patients with interferon early on in their infection, could help increase expression of SETDB2 and prevent this complication. For diabetes patients who are hospitalized for COVID, however, treatment with interferon is currently not recommended by U.S. health officials outside of clinical trials.

Managing diabetes-related complications

When people with diabetes get a viral infection, their risk for potentially deadly diabetes-related complications also increases.

One possible complication is diabetic hyperglycemic hyperosmolar syndrome, which occurs when the kidneys get rid of extra blood sugar through the urine, leading to dehydration. Once a patient becomes dehydrated, the kidneys are no longer able to get rid of the extra sugar, allowing it to accumulate to extremely high levels in the blood. The amount of salt, sugar and other substances in the blood also becomes more concentrated, which pulls water out of vital organs, including the brain.

The risk for DKA (diabetic ketoacidosis) also increases. DKA occurs when the body lacks enough insulin to usher sugar from the blood into cells where it can be used for energy. As a result, the body begins to burn fat for energy, which produces chemicals called ketones. As these ketones accumulate in the blood, it becomes more acidic.

DKA is dangerous on its own but if you have COVID, it can also make it more difficult to manage complications associated with the disease, including sepsis.

Diabetes also increases the risk for a slew of other serious health issues, including heart and kidney disease as well as stroke. It’s possible that these diabetes-related conditions may also play a role in worse outcomes among people with COVID.

“There are a lot of underlying risks that patients bring in addition to their diabetes,” Eckel says.

How to protect yourself

Everyone should continue to take precautions to prevent the spread of COVID. This includes being fully vaccinated, which includes getting a booster as soon as you’re eligible.

Wash your hands well and often with soap and water and avoid touching your face with unclean hands.

If you have diabetes, wearing a mask, particularly in crowded indoor spaces or areas with poor ventilation is still a good idea. It’s also essential be vigilant about following your treatment plan and maintaining strict control of your blood sugar levels—checking it regularly or as often as your doctor recommends.

Call your doctor if your blood sugar level stays above 250 mg/dL. If you have type 1 diabetes and your blood sugar rises above this level, you could be at risk for DKA.

Other precautions you should take:

• Stock up on your medication and essential supplies. Make sure you have enough prescription medications and give yourself plenty of time to get refills.
• Keep essentials on hand. This may include glucose tablets and testing strips as well as syringes or insulin pen or pump supplies, including batteries and alcohol swabs, Nadolsky advises. Check with your pharmacy to find out if the items you need could be mailed to your home.
• Adhere to your treatment plan. Do not stop taking any of your prescriptions unless your doctor instructs you to do so. This is true even if you’re taking angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). The American College of Cardiology, the American Heart Association, the Heart Failure Society of America, and the European Society of Cardiology have all issued guidelines saying patients should not stop taking these drugs, pointing out that there is no evidence to suggest they could contribute to more severe COVID cases.
• Try to stick to your routine. Maintaining a healthy diet and keeping up with your exercise regimen can help keep your blood sugar levels in a normal range, Eckel advises. The immune system is better to able to fight infection when blood sugar levels are under control than when they are high, he adds.
• Don’t skip your check-ups. It’s important to stay in touch with your doctor and keep all necessary follow up appointments. Telemedicine has emerged as a valuable tool for doctors and patients. The ability to talk to your doctor and discuss your concerns virtually—or by video conference on your smartphone, tablet, or computer—can help you manage your condition.