For a person living with diabetes, an infection creates a dangerous metabolic situation. The presence of a pathogen triggers a stress response that causes blood glucose levels to rise significantly, regardless of food intake. This high glucose impairs the body’s ability to mount an effective defense, trapping the individual in a cycle of worsening infection and uncontrolled blood sugar. An untreated infection can quickly spiral into a life-threatening diabetic emergency, requiring specific management strategies.
How Infections Skyrocket Blood Sugar Levels
When the body detects an infection, it initiates a “fight or flight” stress response to mobilize energy for defense. This reaction involves the rapid release of counterregulatory hormones, including cortisol, adrenaline, and glucagon. These hormones increase the amount of glucose in the bloodstream by signaling the liver to dump stored reserves (glycogenolysis) and create new glucose (gluconeogenesis).
The surge of stress hormones also dramatically increases insulin resistance throughout the body. Cells become less responsive to existing insulin, meaning glucose cannot effectively move out of the blood. For a person with diabetes, whose insulin utilization is already compromised, this combination leads to severe and persistent hyperglycemia. Even if a person stops eating, their blood sugar remains dangerously high because the liver continually produces glucose.
Why Diabetics Are More Prone to Infection
Chronic high blood glucose levels compromise the body’s natural defenses, making it easier for infections to take hold and harder to clear them. Hyperglycemia directly impairs the function of white blood cells, such as neutrophils and macrophages. Specifically, the ability of these cells to engulf and destroy invading bacteria (phagocytosis) is significantly reduced when blood sugar is elevated. This dysfunction makes the immune response slower and less effective at controlling the initial spread of a pathogen.
Diabetes often leads to damage in the circulatory and nervous systems. Poor blood circulation, particularly in the extremities, limits the delivery of immune cells and antibiotics to the infection site. Nerve damage (neuropathy) can prevent an individual from feeling a minor injury, allowing a small wound to progress unnoticed into a severe ulcer and deep-tissue infection. These factors explain the increased incidence of common infections like urinary tract infections, skin infections, and candidiasis.
Recognizing Severe Complications: DKA and HHS
Uncontrolled hyperglycemia during an infection can rapidly lead to two distinct and life-threatening emergencies: Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS).
Diabetic Ketoacidosis (DKA)
DKA is most often seen in people with type 1 diabetes, where a near-total lack of insulin forces the body to break down fat for fuel. This fat breakdown produces an excess of acidic byproducts called ketones, which accumulate in the blood, leading to metabolic acidosis. Symptoms develop quickly, often within 24 hours, and include nausea, vomiting, abdominal pain, and a distinct fruity odor on the breath caused by exhaled ketones. Another distinguishing sign is Kussmaul breathing, which is deep, rapid breathing used to expel the excess acid. Diagnosis typically occurs when blood glucose is above 250 mg/dL, accompanied by high levels of ketones.
Hyperosmolar Hyperglycemic State (HHS)
HHS is more common in older individuals with type 2 diabetes and develops insidiously over several days to weeks. In HHS, there is enough residual insulin to prevent the large-scale production of ketones, but not enough to control blood sugar. This results in extreme hyperglycemia, often exceeding 600 mg/dL, which pulls massive amounts of water from the body’s cells into the bloodstream. The severe dehydration and resulting hyperosmolality are the primary dangers, leading to symptoms like profound thirst and an altered mental state, which can progress to coma. Both conditions require immediate medical intervention, but HHS generally has a higher mortality rate.
Immediate Steps and Sick Day Management
A structured sick day management plan is necessary for any person with diabetes dealing with an illness. Insulin therapy must never be stopped, even if the person is unable to eat. Basal insulin is required to suppress the liver’s glucose production, which is ramped up by stress hormones.
Monitoring frequency must increase significantly, with blood glucose checked every three to four hours. If levels are consistently above 240 mg/dL, or if vomiting is present, the person must check for ketones using blood or urine strips. Proper hydration is paramount, requiring the consumption of 6 to 8 ounces of fluid every hour to prevent severe dehydration.
Immediate contact with a healthcare provider is necessary if a person experiences any of the following:
- Persistent vomiting.
- A high fever.
- Inability to keep fluids down for several hours.
- A blood ketone level above 1.5 mmol/L or sustained blood glucose above 250 mg/dL.
Patients taking SGLT2 inhibitor medications must stop the medication immediately upon illness due to the risk of euglycemic DKA, which can occur even with normal or mildly elevated glucose levels.