When a person with diabetes contracts an infection, the body initiates a complex physiological response that significantly complicates blood sugar management. This interaction creates a challenging cycle: the infection disrupts glucose control, and the resulting high blood sugar weakens the body’s ability to fight the pathogen. Individuals with diabetes face a higher risk of developing infections, experiencing more severe outcomes, and requiring longer recovery periods compared to the general population. Understanding this reciprocal relationship is key to safely navigating illness while managing diabetes.
The Physiological Impact of Infection on Glucose Control
The body’s defense against any infection triggers a severe stress response, which is the primary driver of rapid blood sugar elevation. This response involves the release of counter-regulatory hormones, such as cortisol and adrenaline (epinephrine), designed to mobilize energy stores to fight the illness. These hormones instruct the liver to produce more glucose and simultaneously cause the body’s cells to become temporarily resistant to insulin.
The result is a condition called “stress hyperglycemia,” where blood glucose levels can spike dramatically, even if the person is eating less. This increased insulin resistance means the usual dose of insulin or oral medication is no longer sufficient to move glucose out of the bloodstream. This metabolic shift ensures energy is available for the immune system but quickly leads to uncontrolled high blood sugar for a person with diabetes.
Conversely, chronic high blood sugar directly compromises the effectiveness of the immune system, creating a cycle that prolongs the infection. Elevated glucose impairs the function of white blood cells, particularly neutrophils, which are the body’s first responders. High glucose levels reduce the ability of these cells to migrate to the site of infection and kill invading microbes, blunting the immune response. Hyperglycemia also promotes chronic inflammation, hindering the body’s effectiveness at clearing the infection and delaying wound healing.
Common High-Risk Infections in Diabetes
People with diabetes are generally more susceptible to infections and often experience more severe forms of common illnesses like influenza and pneumonia. The risks are particularly high for certain infections due to the underlying effects of diabetes on circulation and nerve function. Infections that are minor for others can quickly become serious complications.
Skin and soft tissue infections are common due to poor circulation and immune impairment, ranging from simple cellulitis to more severe abscesses. Fungal infections, such as oral and vaginal candidiasis, also occur more frequently, as high glucose provides a favorable environment for fungal growth. Slow-healing wounds are a major concern because impaired immune response and poor blood flow delay the repair process, increasing the risk of persistent infection.
Urinary tract infections (UTIs) present an increased risk, including severe kidney infections. High glucose levels in the urine create an ideal breeding ground for bacteria, and nerve damage can impair the bladder’s ability to empty completely. Diabetic foot infections are especially concerning, often stemming from minor injuries that go unnoticed due to nerve damage (neuropathy). Combined with reduced blood supply, these infections can rapidly progress to deep tissue involvement or bone infection (osteomyelitis), frequently requiring aggressive medical or surgical intervention.
Recognizing Diabetic Ketoacidosis and Hyperosmolar Hyperglycemic State
Infection is a frequent trigger for two serious acute complications of diabetes: Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS). Both conditions are medical emergencies requiring immediate, professional treatment.
Diabetic Ketoacidosis (DKA)
DKA most commonly affects individuals with Type 1 diabetes, but can also occur in those with Type 2 diabetes. DKA develops when there is a severe lack of insulin, forcing the body to break down fat for energy, which produces acidic byproducts called ketones. The build-up of these ketones causes the blood to become dangerously acidic. Warning signs often develop rapidly, sometimes within 24 hours.
Symptoms include:
- Extreme thirst and frequent urination
- Nausea, vomiting, and abdominal pain
- Kussmaul breathing (deep, rapid, gasping breaths)
- Breath with a characteristic fruity or acetone odor
Hyperosmolar Hyperglycemic State (HHS)
HHS primarily affects older adults with Type 2 diabetes and develops more gradually over days or weeks. It is characterized by extremely high blood glucose levels, often exceeding 600 mg/dL, without significant ketone production. The high glucose causes excessive urination and severe dehydration, leading to highly concentrated blood. Symptoms include profound thirst, confusion, lethargy, and sometimes temporary neurological signs like weakness or blurred vision. Any sign of severe confusion or altered consciousness warrants an immediate call for emergency medical services.
Essential Sick Day Management for Diabetics
A clear plan for managing diabetes during illness is essential to prevent acute complications triggered by infection. When feeling unwell, individuals should increase the frequency of blood glucose monitoring to every two to four hours, even overnight, as levels can change quickly. For those with Type 1 diabetes or those taking certain medications, checking for ketones is necessary if blood sugar is persistently high (e.g., over 250 mg/dL).
Maintaining hydration is a top priority, as high blood sugar causes fluid loss through increased urination. Drinking plenty of non-alcoholic, non-caffeinated fluids every hour is important to prevent dehydration and help flush out excess glucose. If solid food cannot be tolerated, consuming carbohydrate-containing fluids like juice or regular soda may be necessary to prevent low blood sugar, especially if taking insulin.
Never stop taking insulin, even if appetite is poor, because the stress hormones will continue to raise blood sugar. Medication adjustments, such as increasing the dose of long-acting or basal insulin, may be needed to overcome insulin resistance, but this requires consultation with a healthcare provider. Certain non-insulin medications, like Metformin or SGLT2 inhibitors, may need to be temporarily stopped during severe illness, vomiting, or diarrhea; patients should seek guidance from their doctor regarding these changes.
Immediate professional medical attention is required if you experience “red flags.” These include:
- Being unable to keep fluids down for more than four hours
- Having a persistent high fever
- Experiencing persistent vomiting or severe diarrhea
- Any symptoms of DKA or HHS, such as severe abdominal pain or confusion
- Inability to bring high blood sugar or ketones down