Diabetes is a chronic condition that requires constant attention to maintain stable blood glucose levels. When a person with diabetes contracts a severe infection, the body’s metabolic system comes under strain, often leading to a temporary loss of control. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19, frequently triggers a surge in blood sugar, resulting in hyperglycemia. This spike in glucose levels complicates the infection and increases the risk of severe health outcomes. Understanding the biological reasons behind this glucose disruption and how to manage it during and after the illness is important.
The Acute Effect on Glucose Control
The infection’s intense physiological response is the primary driver of high blood sugar. When the body encounters SARS-CoV-2, it initiates a massive inflammatory reaction known as the cytokine storm. These inflammatory proteins interfere directly with insulin action, a phenomenon called insulin resistance. This causes cells in the liver, muscle, and fat tissue to ignore insulin’s signal to absorb glucose.
The physical stress of fighting the infection also activates the body’s “fight or flight” response. This triggers the release of counter-regulatory hormones such as cortisol and adrenaline. These hormones instruct the liver to produce and release more glucose, providing the body with immediate energy. This dual assault—reduced insulin effectiveness combined with increased glucose production—causes blood sugar levels to rise rapidly.
Some research suggests the virus may directly affect the organs responsible for glucose regulation. SARS-CoV-2 uses the ACE2 receptor to enter cells, and this receptor is present on the insulin-producing beta cells within the pancreas. While direct viral damage is debated, the combination of systemic inflammation and stress hormones represents the dominant mechanism for acute loss of glucose control during active COVID-19 illness.
Practical Steps for Managing Blood Sugar During Illness
Managing diabetes during an acute COVID-19 infection requires a “sick day” plan emphasizing frequent monitoring and hydration. People with diabetes should check their blood glucose levels more often than usual, ideally every two to four hours. They should also test for ketones if they have type 1 diabetes or if blood sugar is consistently high, as glucose levels can fluctuate widely and rapidly during illness.
Staying well-hydrated is important, as sufficient fluid intake helps the body flush out excess glucose and ketones. If blood sugar levels are high, non-caloric liquids like water or diet soda are appropriate. Low blood sugar requires small, frequent sips of carbohydrate-containing fluids like fruit juice. Do not stop taking insulin, even if appetite is low, as the body requires basal insulin to counteract stress hormones and inflammation.
Adjustments to insulin or other medication dosages should only be made in consultation with a healthcare provider. Contact a doctor immediately if persistent high blood sugar readings occur, or if signs of a metabolic emergency are noticed, such as diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS). These signs include:
- Deep, rapid breathing.
- Excessive thirst and urination.
- Severe nausea or vomiting.
- A fruity odor on the breath.
Can COVID-19 Cause Diabetes in Healthy Individuals
Beyond worsening pre-existing conditions, a concern is the emergence of new-onset diabetes following a COVID-19 infection in people with no prior history of the disease. Researchers have observed an increased number of new diabetes diagnoses in the months following SARS-CoV-2 infection. One explanation is that the infection unmasks pre-existing, undiagnosed pre-diabetes by placing severe stress on the metabolic system.
However, the virus may also play a direct role in some cases. The inflammatory response and potential direct infection of pancreatic cells could initiate an autoimmune process that damages the insulin-producing beta cells. This mechanism is similar to how other viral infections are thought to trigger type 1 diabetes.
The severity of the initial infection may influence the risk, as severe inflammatory responses place the greatest strain on the pancreas’s ability to produce insulin. Researchers are still working to determine how often this new-onset diabetes is permanent, or if it is a transient condition that resolves after recovery. For some people, the infection acts as a strong catalyst that accelerates the development of the condition.
Monitoring Glucose Levels After Recovery
Vigilance does not end when acute COVID-19 symptoms resolve. Many individuals experience persistent difficulties with glucose control in the weeks and months following the infection, often referred to as “Post-COVID hyperglycemia.” This continued elevation and instability in blood sugar can last for several months.
Individuals should return to their standard monitoring schedule and discuss their recovery with their diabetes care team. A follow-up visit should include an HbA1c test, which measures average blood glucose over the previous two to three months, to assess the long-term impact. If blood sugar remains elevated, a healthcare provider may need to reassess and adjust baseline medication or insulin requirements.
Adopting positive lifestyle changes, such as a fiber-rich diet and regular physical activity, can help restore metabolic balance. Continued monitoring of blood glucose and HbA1c levels is recommended for several months following the infection to ensure the metabolic disruption has fully stabilized.