When an illness strikes, the body’s natural defense mechanisms can alter its ability to manage blood sugar, leading to stress-induced hyperglycemia. Being sick can raise blood sugar, even in people without diabetes. This temporary biological response pushes glucose levels higher as the body fights infection or injury. While anyone can experience this rise, it creates a significant health hazard for individuals with pre-existing diabetes, requiring careful monitoring and proactive management during sickness.
How Illness Triggers High Blood Sugar
The primary reason for elevated blood sugar during sickness is the body’s defensive reaction to stress, orchestrated by the immune system. When the body detects infection or physical stress, it releases counter-regulatory hormones designed to mobilize energy reserves. These hormones include cortisol, adrenaline (epinephrine), and glucagon, which work against the effects of insulin.
These hormones achieve their effect through two main processes in the liver. They increase gluconeogenesis, the creation of new glucose from non-carbohydrate sources like protein and fat. They also accelerate glycogenolysis, the breakdown of stored glucose (glycogen) back into usable glucose. Both processes flood the bloodstream with large amounts of sugar, providing immediate fuel to combat the illness.
Simultaneously, the stress hormones cause temporary insulin resistance in muscle and fat tissues. This makes the body’s cells less responsive to insulin, making it difficult for glucose to leave the bloodstream and enter the cells for energy. The resulting imbalance—high glucose production combined with reduced glucose uptake—causes a rapid elevation in blood sugar levels. This effect can occur even if a person is not eating normally.
Emergency Complications of High Blood Sugar During Sickness
For individuals with diabetes, particularly Type 1, high glucose and insufficient insulin action during illness can quickly lead to Diabetic Ketoacidosis (DKA). DKA occurs when the lack of usable glucose forces the body to break down fat for energy, producing acidic byproducts called ketones. These ketones build up in the blood, causing it to become highly acidic, which can be fatal if not treated immediately.
A separate, severe complication is Hyperosmolar Hyperglycemic State (HHS), which is more common in Type 2 diabetes. While residual insulin usually prevents large-scale ketone production, HHS is characterized by extreme high blood sugar levels, often exceeding 600 mg/dL, and severe dehydration. The high concentration of sugar pulls fluid out of the body’s cells, leading to volume depletion and hyperosmolarity.
Warning signs for DKA include persistent nausea, vomiting, abdominal pain, and a fruity odor on the breath caused by excess ketones. HHS typically develops slowly, presenting with neurological symptoms like lethargy, confusion, or seizures. Any sign of extreme illness, especially high blood sugar that does not respond to standard treatment, warrants immediate emergency medical attention.
Sick Day Management Guidelines
When illness strikes, individuals managing diabetes must follow a proactive plan to prevent complications.
Monitoring Glucose and Ketones
Monitoring blood glucose levels must be increased significantly, often requiring checks every two to four hours, even throughout the night. This frequent testing provides the necessary data to make timely adjustments to medication and fluid intake. Testing for ketones is necessary, especially for those with Type 1 diabetes or when blood sugar levels remain above 240 mg/dL. The presence of moderate to large amounts of ketones signals that DKA may be developing and requires immediate contact with a healthcare provider.
Hydration and Nutrition
Maintaining adequate hydration is paramount, as illness and high blood sugar both accelerate fluid loss. Drinking small amounts of sugar-free fluid, such as water or broth, every hour is recommended to combat dehydration. If unable to eat solid food, consume small amounts of carbohydrate-containing liquids to prevent hypoglycemia, which can occur with certain diabetes medications.
Medication Adjustments
Medication management during sickness must be handled with caution and consultation from a medical professional. Individuals on insulin must never stop taking their long-acting or basal insulin, even if they are not eating, as this foundational dose prevents DKA. Adjustments to short-acting insulin or oral medications, including temporarily stopping drugs like SGLT2 inhibitors or metformin in cases of severe vomiting, should only be done under a doctor’s guidance. Persistent vomiting for more than four hours, a high fever, or blood sugar remaining high despite multiple corrective doses are reasons to call a healthcare provider or seek urgent care.