A common physiological response to illness, including viral infections like a cold or the flu, is a temporary rise in blood sugar, a condition known as stress hyperglycemia. This elevation is not limited to individuals who already have diabetes; it can occur in anyone as the body mobilizes its defenses to fight the invading pathogen. When the immune system detects a virus, it initiates a complex cascade of hormonal and inflammatory signals designed to fuel the fight and restore balance.
The Body’s Stress Response and Glucose Elevation
A viral infection triggers a profound stress response in the body, which is the primary driver of glucose elevation. When the body is under attack, the adrenal glands release high levels of stress hormones, particularly cortisol and adrenaline (epinephrine). These hormones are part of the body’s “fight or flight” mechanism, serving to ensure that energy is immediately available to the immune system and other vital organs.
Adrenaline and cortisol act directly on the liver, stimulating gluconeogenesis (the creation of new glucose) and glycogenolysis (the breakdown of stored glycogen). This action floods the bloodstream with fuel, resulting in a rapid increase in circulating blood sugar. The immune system’s primary cells, such as macrophages and neutrophils, rely heavily on glucose for energy, making this elevated supply necessary for the immune response.
The second major mechanism involves systemic inflammation. The immune system releases signaling proteins called cytokines to coordinate the antiviral defense. Pro-inflammatory cytokines, such as Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-α), disrupt the normal function of insulin, leading to temporary insulin resistance. This resistance means that the body’s cells do not respond effectively to insulin, causing glucose to remain in the bloodstream instead of being taken up for energy.
How Viral Infections Affect Different Individuals
The consequences of this infection-induced hyperglycemia vary significantly depending on an individual’s existing metabolic health. For individuals without a pre-existing diagnosis of diabetes, the rise in blood sugar is typically transient and well-managed by a healthy pancreas. Their pancreas is able to compensate for the temporary insulin resistance by secreting a greater amount of insulin, which eventually brings the blood glucose level back down to a normal range. While the blood sugar may be temporarily elevated, it rarely reaches dangerous levels or causes long-term complications.
The situation is more concerning for individuals who have diagnosed diabetes, whether Type 1 or Type 2, because their body’s ability to manage glucose is already impaired. For those with Type 2 diabetes, the combination of stress hormones, inflammation, and pre-existing insulin resistance can lead to dangerously high blood sugar that is difficult to control. The inability to overcome the temporary resistance may require significant medication adjustments, even for minor illnesses.
Individuals with Type 1 diabetes face the highest risk, as their pancreas produces little to no insulin to counteract the blood sugar spike. Without sufficient insulin, the body begins to break down fat for fuel, which produces acidic byproducts called ketones. This process can rapidly progress to diabetic ketoacidosis (DKA), a life-threatening medical emergency characterized by a buildup of ketones and dangerously high blood sugar. Any viral illness increases the risk of DKA in this population.
Essential Steps for Managing Blood Sugar While Sick
Effective management of blood sugar during a viral infection requires proactive planning, particularly for those with diabetes, following what are known as “sick day rules.” A fundamental step is to increase the frequency of blood glucose monitoring to every two to four hours, even if appetite is low or the individual is not eating normally. This frequent testing provides the necessary data to make timely adjustments and identify dangerous trends early.
Hydration is another essential element, as high blood sugar can increase urination and lead to rapid dehydration. It is recommended to drink a cup of fluid every hour while awake, prioritizing sugar-free options like water or broth for primary hydration. However, if blood sugar levels are low or if the individual cannot keep down solid food, small amounts of carbohydrate-containing fluids, such as half a cup of regular soda or juice, should be consumed to prevent hypoglycemia and ketone production.
Medication management should always involve consultation with a healthcare provider, but some general principles apply. Individuals taking insulin should never stop their injections, as the body still needs insulin to prevent DKA, even if they are not eating. Doses may need to be increased to combat the infection-induced insulin resistance, or adjusted downward if the individual is experiencing low blood sugar from poor appetite.
There are specific warning signs that necessitate immediate medical attention. These symptoms may indicate severe dehydration or the onset of DKA, which requires hospital treatment to stabilize.
- Testing for ketones is mandatory for individuals with Type 1 diabetes when blood sugar is persistently high (above 240 mg/dL) or during any illness.
- Persistent vomiting.
- An inability to keep down fluids.
- A high fever (over 101°F).