Infection increases blood sugar levels as a response by the body to combat illness. When the immune system is activated to fight off a pathogen, it unleashes a cascade of hormones designed to prepare the body for stress and supply energy to immune cells. This defense mechanism is potent enough to elevate glucose concentrations even if a person is eating less than usual or fasting.
How the Immune System Triggers Glucose Spikes
The body perceives an infection as a significant physical stressor, which immediately activates the hormonal stress response system. This activation leads to the rapid release of counter-regulatory hormones, primarily cortisol, adrenaline (epinephrine), and glucagon. These hormones are naturally opposed to the action of insulin.
Simultaneously, the immune system releases inflammatory signaling molecules known as cytokines. These cytokines further amplify the metabolic disruption by promoting a state of temporary insulin resistance throughout the body. The combined effect of stress hormones and inflammatory cytokines reduces the ability of muscle and fat cells to absorb glucose from the blood.
The liver, under instruction from the stress hormones, increases its output of glucose through a process called gluconeogenesis. This surge in production, coupled with the reduced uptake of glucose by peripheral tissues, leads directly to elevated blood sugar concentrations. This glucose spike is an attempt to fuel the immune response, but for individuals managing blood sugar, it can lead to concerning levels of hyperglycemia.
Managing Blood Sugar During Illness
Managing elevated glucose concentrations while sick requires a proactive approach, particularly for individuals with diabetes. The immediate priority is to increase the frequency of blood glucose monitoring, checking levels at least every two to four hours, even during the night. This frequent testing provides a dynamic picture of how the body is responding to the illness and allows for timely adjustments.
Maintaining adequate hydration is important, as high blood sugar promotes increased urination, which can quickly lead to dehydration. Individuals should consume sugar-free fluids like water or broth to replace lost fluids and electrolytes. Even if appetite is diminished, it is generally recommended to continue taking usual diabetes medications, especially long-acting basal insulin, but specific adjustments should always be discussed with a healthcare provider.
For those who rely on insulin, the dosage will almost certainly need adjustment because of the heightened insulin resistance caused by the infection. Healthcare providers may advise using supplemental doses of rapid-acting insulin to correct high blood sugar readings, often based on a pre-established scale. Never stop taking insulin entirely, as this drastically increases the risk of severe complications.
Checking for ketones in the blood or urine is necessary, particularly if blood sugar levels are persistently elevated above 240 mg/dL or 13.3 mmol/L. Ketones are byproducts of fat breakdown, indicating the body is burning fat for energy due to a lack of usable glucose. The presence of ketones requires immediate action, as it signals a shift toward a more dangerous metabolic state.
Recognizing Emergency Warning Signs
Certain symptoms during an illness indicate a medical emergency and require immediate professional attention. These severe complications include Diabetic Ketoacidosis (DKA) and Hyperglycemic Hyperosmolar State (HHS), both of which are life-threatening. DKA, more common in type 1 diabetes, results from a severe lack of insulin and a high concentration of ketones.
Warning signs of DKA include persistent vomiting, deep and rapid breathing (Kussmaul respiration), and a distinct fruity odor on the breath. Other symptoms are severe abdominal pain, extreme fatigue, and mental confusion. If an at-home test shows blood ketone levels at or above 3.0 mmol/L, or if blood sugar remains above 300 mg/dL despite management, emergency care should be sought immediately.
HHS, which is more common in type 2 diabetes, involves extremely high blood sugar levels, often exceeding 600 mg/dL, and severe dehydration without significant ketone production. Symptoms often develop more slowly and include profound thirst, confusion, hallucinations, or loss of consciousness. Any inability to keep fluids down for several hours, or a high fever that will not break, also warrants prompt medical evaluation to prevent these severe outcomes.