When a person with diabetes becomes ill—whether with a common cold, the flu, or an infection—their blood sugar levels almost always rise, a situation known as “sick day management.” This phenomenon occurs even when the individual is eating little or no food. Understanding the body’s natural defense mechanisms during illness is the first step in managing this temporary but potentially dangerous state of high blood sugar. Because every person’s condition and treatment plan are unique, it is recommended to consult with a healthcare provider to establish a personalized sick day plan before an illness occurs.
The Physiological Response to Illness
An acute illness triggers a powerful defense response involving the rapid release of several stress hormones, such as cortisol, adrenaline (epinephrine), and glucagon. These hormones are secreted to help the body fight the infection and mobilize energy reserves. This hormonal surge is the primary reason blood sugar levels climb during sickness.
These stress hormones signal the liver to increase its production and release of stored glucose into the bloodstream, essentially flooding the body with fuel. Simultaneously, the hormones cause increased insulin resistance, making cells in the muscles and fat tissue less responsive to available insulin. This dual action—increased glucose production and reduced glucose uptake—results in a rapid and sustained rise in blood sugar, even with a reduced appetite.
Critical Monitoring and Testing
During any illness, the frequency of monitoring blood glucose must increase significantly to guide necessary adjustments. It is advised to check blood sugar levels at least every two to four hours, and sometimes more often, including during the night. Close monitoring is necessary because glucose levels can fluctuate rapidly and unexpectedly when the body is fighting an infection.
Testing for ketones is equally important, especially when blood sugar levels are elevated, typically above 250 mg/dL. Ketones are acidic byproducts that form when the body, lacking sufficient insulin to process glucose for energy, begins breaking down fat instead. The presence of ketones indicates a serious lack of effective insulin and can signal the onset of a life-threatening complication.
Ketone levels can be checked using either urine strips or a blood ketone meter; the latter provides a more current and precise reading. Ketone results are categorized, and knowing the difference is important for determining the urgency of the situation. For instance, a blood ketone level above 1.5 mmol/L is often a cause for concern, while a level above 3.0 mmol/L indicates a medical emergency requiring immediate attention. The goal of monitoring is to catch rising glucose and ketone levels early, allowing for timely intervention.
Guidelines for Medication and Hydration Adjustment
Managing diabetes medications during illness requires careful adjustments based on frequent monitoring. For individuals using insulin, the background or basal dose of long-acting insulin must never be stopped, even with minimal food intake. The increased insulin resistance caused by stress hormones means that the need for basal insulin may actually increase, rather than decrease, to suppress the liver’s excessive glucose production.
Correction doses of rapid-acting insulin will likely need to be increased and administered more frequently to address persistent high blood sugar. This supplemental insulin is given in addition to any mealtime doses. Some sick day plans advise a set percentage increase over the total daily dose to overcome temporary insulin resistance.
Oral Medication Adjustments
For those on oral medications, a healthcare provider may advise temporarily stopping certain drugs. Metformin may be stopped due to the increased risk of lactic acidosis if the patient is dehydrated. SGLT2 inhibitors (like canagliflozin or empagliflozin) must be stopped immediately during any acute illness due to the heightened risk of a specific type of ketoacidosis.
Hydration
Hydration is an important component of sick day management, as both illness and high blood sugar lead to fluid loss. Drinking plenty of non-caloric fluids, such as water or broth, is necessary to prevent dehydration and help the kidneys flush out excess glucose and ketones. If the individual is struggling to eat, small amounts of carbohydrates can be consumed to maintain energy and prevent hypoglycemia that might result from increased insulin doses. Sources include crackers, toast, or clear sugary drinks. It is important to aim for a consistent intake of fluids and small amounts of carbohydrates to stabilize the body’s metabolic state while the illness runs its course.
Recognizing Signs of Emergency
While most sick days can be managed at home, certain symptoms indicate the need for immediate medical intervention. The main concerns are two acute, life-threatening complications: diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS). DKA, more common in Type 1 diabetes, results from a severe lack of insulin leading to a dangerous buildup of ketones and blood acidity.
Signs of DKA include persistent nausea and vomiting, deep and rapid breathing (Kussmaul breathing), abdominal pain, and a fruity odor on the breath caused by elevated ketones. HHS, more common in Type 2 diabetes, is characterized by extreme dehydration and severely high blood sugar, often exceeding 600 mg/dL, without high ketone levels. Symptoms of HHS often involve neurological changes, such as confusion, drowsiness, or an altered mental state. Any sign of these severe symptoms, or an inability to keep fluids down, warrants an urgent call to emergency services.