The Connection Between Infection and Blood Sugar Dysregulation

Diabetes management hinges on maintaining stable blood glucose levels, a task that becomes markedly more difficult when an infection arises. For the millions of people using diabetic lenses—non-invasive continuous glucose monitoring contact lenses—this challenge is compounded by the potential for the infection itself to compromise the accuracy and comfort of the device. Understanding the physiological interplay between infection and glucose metabolism is essential for both healthcare providers and patients aiming to reduce complication risks and maintain optimal health outcomes.

When the body confronts a pathogen, the immune system mounts a coordinated response. This response includes the release of stress hormones such as cortisol and epinephrine, along with pro-inflammatory cytokines. These chemical signals are designed to mobilize energy stores to fight the invader, but they also directly antagonize insulin action, leading to transient insulin resistance. For a person with diabetes, even a minor infection such as a common cold or urinary tract infection can cause blood sugar levels to spike unpredictably, demanding more frequent monitoring and adjustments to therapy. The metabolic derangement can persist for days after symptoms resolve, requiring continued vigilance.

This article explores how infections disrupt blood sugar control, the unique vulnerabilities faced by diabetic lens users, and evidence-based strategies to navigate illness while maintaining optimum glucose management. It also addresses preventive measures and the role of emerging sensor technologies in improving outcomes during sick periods.

The Physiological Disruption: How Infections Elevate Blood Glucose

The body’s response to infection is orchestrated by the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Cortisol, often called the stress hormone, increases hepatic gluconeogenesis and decreases peripheral glucose uptake, effectively raising blood sugar. Similarly, epinephrine prompts glycogenolysis in the liver and muscles, releasing stored glucose into the bloodstream. These actions, while beneficial for providing quick energy to immune cells, create a metabolic storm that can be particularly hazardous in diabetes.

In addition to hormonal changes, infection triggers a robust inflammatory response. Cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) promote insulin resistance by impairing insulin signaling in muscle and fat tissue. This inflammation-induced insulin resistance can persist even after the acute symptoms of infection subside, sometimes requiring several days for glucose metabolism to return to baseline. The magnitude of the glycemic response often correlates with the severity of the infection—mild upper respiratory infections may cause only modest elevations, while sepsis can trigger extreme hyperglycemia or even hypoglycemia due to metabolic exhaustion.

It is also worth noting that the fever associated with infection can lead to dehydration, which concentrates blood glucose and stresses the kidneys. Dehydration reduces the body’s ability to excrete excess glucose through urine, further contributing to hyperglycemia. Conversely, severe infections can occasionally trigger hypoglycemia if the patient is unable to eat or if medication absorption changes. Patients on insulin or sulfonylureas are especially vulnerable to hypoglycemic episodes during periods of reduced food intake, and the typical symptoms of infection (nausea, vomiting, diarrhea) can mimic or mask low blood sugar signs.

For a detailed review of the hormonal and inflammatory pathways involved, consider the American Diabetes Association’s resources on sick day management and the CDC guidelines for managing illness with diabetes. These resources also emphasize that tight glucose control before and during illness reduces the risk of complications such as diabetic ketoacidosis and hyperosmolar hyperglycemic state.

Common Infections That Significantly Impact Blood Sugar

While any infection can disrupt glucose control, certain types are more frequently associated with pronounced metabolic derangements in diabetic individuals. Understanding these patterns helps patients and clinicians prioritize prevention and early intervention.

  • Urinary Tract Infections (UTIs): Diabetics are at higher risk for UTIs due to glycosuria and impaired immune function. Asymptomatic bacteriuria can progress to pyelonephritis, causing systemic inflammation and severe hyperglycemia. Blood sugar may remain elevated until the infection is completely cleared. Women with diabetes are particularly susceptible, and recurrent UTIs can lead to chronic low-grade inflammation that worsens glycemic control over time.
  • Respiratory Infections: Influenza, COVID-19, and other viral respiratory infections are well-known precipitants of glucose excursions. The systemic inflammatory response can induce profound insulin resistance, and the use of corticosteroids for treatment (e.g., for COVID-19) adds another layer of complexity. Pandemic data showed that diabetic patients with COVID-19 had higher rates of hyperglycemia and worse outcomes, underscoring the importance of vaccination and early antiviral therapy when indicated.
  • Skin and Soft Tissue Infections: Diabetic foot infections, cellulitis, and abscesses are common. Local infections can become systemic if not treated promptly, leading to a hyperglycemic crisis such as diabetic ketoacidosis (DKA) in type 1 diabetes or hyperosmolar hyperglycemic state in type 2 diabetes. Neuropathy and peripheral vascular disease in diabetes increase the risk of unnoticed injuries that become infected.
  • Dental Infections: Periodontitis and periapical abscesses contribute to chronic low-grade inflammation, which worsens insulin resistance. Acute dental infections can also trigger sharp rises in blood glucose. Diabetic patients with untreated periodontal disease often have higher A1C levels, and successful periodontal treatment has been shown to improve glycemic control moderately.

Recognizing these infection types and their typical glycemic impact allows patients and clinicians to be proactive in adjusting monitoring and treatment. Early antibiotic therapy, when appropriate, can help shorten the duration of hyperglycemia.

Diabetic Lens Technology: Promise and Peril During Illness

Diabetic lenses represent a frontier in non-invasive glucose monitoring. These contact lenses use embedded biosensors to measure glucose concentrations in tear fluid, providing real-time data without fingersticks. When functioning correctly, they offer a convenient and patient-friendly alternative to traditional blood glucose meters. However, their accuracy and usability are challenged during infections, both systemic and ocular. The promise of continuous monitoring must be balanced with an understanding of the device's limitations under physiological stress.

Systemic infections cause edema, or generalized swelling, which can affect the fit of the contact lens on the eye. Even slight changes in corneal curvature or tear composition can alter sensor readings. Moreover, the increased tear protein concentration during illness may foul the sensor surface, leading to drift in glucose measurements. A 2022 study in the Journal of Diabetes Science and Technology found that diabetic contact lens sensors showed greater mean absolute relative difference (MARD) values in subjects with concurrent infections compared to healthy periods. The MARD increased by 5-10% during infections, which could lead to missed hypoglycemic or hyperglycemic events if users rely solely on the lens.

Local eye infections present an even more direct problem. Conjunctivitis, keratitis, or blepharitis can cause photophobia, discharge, and discomfort that make lens wear intolerable. Diabetes itself increases the risk of infectious keratitis, and wearing contact lenses—even smart lenses—during an eye infection can exacerbate the condition and delay healing. Patients must be instructed to remove their diabetic lenses at the first sign of eye redness or pain and switch to a backup monitoring method (such as fingerstick or a continuous glucose monitor [CGM] patch). The American Academy of Ophthalmology recommends that anyone with diabetes who uses contact lenses have a low threshold for discontinuing use during any ocular symptom.

Additionally, the inflammation from an eye infection can cause local vasodilation and increased blood flow, which may transiently affect tear glucose kinetics, further confounding sensor accuracy. Therefore, it is recommended that diabetic lens users maintain a high index of suspicion for sensor inaccuracies during any illness, especially if glucose readings deviate from expected patterns. Keeping a traditional meter as a backup is essential for safe sick-day management.

Special Considerations for Type 1 and Type 2 Diabetes

The impact of infection on blood sugar and lens performance can differ between type 1 and type 2 diabetes. In type 1 diabetes, absolute insulin deficiency means that even small increases in insulin resistance from infection can lead to rapid ketone production and DKA. Lens users with type 1 diabetes should check ketones whenever blood sugar exceeds 240 mg/dL during illness. In type 2 diabetes, the risk of hyperosmolar hyperglycemic state is higher, especially in older adults, and the gradual nature of insulin resistance may allow more time to adjust oral medications. However, lens accuracy issues remain relevant for both groups. Type 2 patients using insulin secretagogues (e.g., sulfonylureas) should be cautious about hypoglycemia if food intake drops, and lens readings should be confirmed with fingersticks in such scenarios.

Managing Blood Sugar During Infection: A Practical Checklist for Lens Users

Maintaining glycemic stability during illness requires a proactive, multi-faceted approach. The following strategies are particularly relevant for individuals using diabetic lenses, as they address both general diabetes sick-day rules and the specific limitations of lens-based monitoring.

  • Increase Monitoring Frequency: Even with a lens sensor, cross-check readings with a traditional blood glucose meter at least every 2–4 hours during the first 48 hours of symptoms. This validates sensor performance and catches discrepancies early. If readings from the lens seem inconsistent with symptoms (e.g., feeling low but lens shows normal), trust the fingerstick over the lens until the situation stabilizes.
  • Follow Sick-Day Medication Protocols: Consult your healthcare provider about temporary adjustments. Type 1 diabetics often need more insulin (both basal and bolus), while type 2 patients may require withholding certain oral hypoglycemic agents like metformin if there is risk of dehydration or renal impairment. Never stop insulin without medical advice. Having a written sick-day plan from your endocrinologist or diabetes educator is invaluable.
  • Test for Ketones: If blood sugar exceeds 240 mg/dL (13.3 mmol/L) or if you are vomiting, test urine or blood ketones. Infection is a common trigger for DKA. Blood ketone meters (measuring beta-hydroxybutyrate) are more accurate and are recommended over urine strips, especially if dehydration is present.
  • Stay Hydrated with Sugar-Free Fluids: Drink at least 8 ounces of water or non-caffeinated, sugar-free beverage every hour. Dehydration worsens hyperglycemia and can accelerate lens drying, increasing discomfort. Electrolyte solutions (zero-sugar versions) may be beneficial if vomiting or diarrhea occurs.
  • Practice Lens Hygiene or Remove Lenses: If your eyes feel dry, gritty, or red, remove the diabetic lenses and clean them according to manufacturer instructions. If symptoms persist, discontinue lens use until fully recovered. Use a backup glucose monitoring device during that time. Do not reuse cleaning solution; always use fresh sterile solution. Consider daily disposable lenses if frequent infections are a concern, but note that most diabetic lenses currently are reusable.
  • Seek Medical Attention Promptly: Warning signs include fever above 101°F (38.3°C) that does not respond to antipyretics, persistent vomiting, difficulty breathing, confusion, or severe headache. Contact your provider if you cannot keep fluids down or if your blood sugar remains above target despite adjustments. For lens users, any eye pain, vision changes, or purulent discharge warrants an immediate eye exam.

Nutritional Support During Illness

Loss of appetite is common during infections, making it difficult to maintain carbohydrate intake. Diabetic lens users should rely on glucose readings to guide consumption. If blood sugar is high, focus on non-starchy vegetables, clear broths, and unsweetened beverages. If blood sugar is low (especially in insulin-dependent patients), consume 15 grams of quick-acting carbohydrate (4 ounces of juice, 1 tablespoon of honey) and recheck after 15 minutes. Avoid sugary sports drinks unless needed for hypoglycemia treatment. For patients with nausea, carbohydrate-containing liquids such as regular broth or glucose gel may be easier to tolerate. A good rule of thumb is to consume at least 50 grams of carbohydrate every 24 hours to prevent starvation ketosis, but this should be individualized based on blood glucose levels.

Preventive Measures: Reducing Infection Risk in the Diabetic Lens Population

Prevention is the most effective strategy for avoiding the cascade of infection-induced hyperglycemia and lens-related complications. Key preventive actions include:

  • Optimal Baseline Glycemic Control: A1C levels below 7% (for most adults) are associated with lower infection incidence. Chronic hyperglycemia impairs neutrophil function and antibody response, making the body more susceptible to pathogens. Each 1% reduction in A1C has been shown to decrease infection risk by approximately 15% in some studies.
  • Vaccinations: Annual influenza vaccine, pneumococcal vaccines (PCV13 and PPSV23), and the COVID-19 vaccine and boosters are strongly recommended. Vaccination reduces the risk and severity of respiratory infections that are particularly disruptive to glucose control. The CDC also recommends the hepatitis B vaccine for diabetic adults under 60. Ensure tetanus, diphtheria, and pertussis (Tdap) vaccinations are up to date.
  • Meticulous Lens Care: Always wash hands before handling diabetic lenses. Use fresh, sterile solution each time. Never top off old solution. Replace the lens case monthly. Do not sleep in lenses unless specifically approved by an ophthalmologist. Diabetic patients with dry eye syndrome may benefit from preservative-free artificial tears (instilled before lens insertion) to reduce the risk of corneal abrasion and subsequent infection.
  • Regular Eye Exams: Diabetic retinopathy and other ocular complications can predispose to infections. Yearly dilated eye exams help detect early changes. Discuss with your eye doctor whether contact lens use is still appropriate if you have recurrent infections or corneal issues. Some patients may be better served by non-lens-based CGMs such as needle-type sensors during periods of frequent illness.
  • Foot and Skin Care: Even if the primary focus is on lenses, systemic infection often begins in the feet or skin. Daily foot inspections, moisturizing dry skin to prevent cracks, and prompt treatment of cuts can prevent infections before they affect the whole body. Peripheral neuropathy may mask pain from early infection, so vigilance is key.

Long-Term Consequences of Repeated Infections on Glycemic Control

Repeated infections can have a cumulative effect on diabetes management. Each episode of infection-induced hyperglycemia may raise A1C by 0.3–0.5% if it lasts more than a few days, and recovery of insulin sensitivity can take weeks. Over the course of a year, multiple infections can shift baseline glucose control upward, leading to increased risk of microvascular complications. For diabetic lens users, the psychological burden of frequent device inaccuracies and removal can also lead to monitoring fatigue, which may reduce adherence during non-illness periods. Therefore, investing in prevention and early treatment of infections is not just a short-term strategy but a long-term investment in diabetes outcomes.

Conclusion

Infections pose a significant threat to blood sugar control in all individuals with diabetes, but they introduce a special set of challenges for those who rely on diabetic lenses for glucose monitoring. The release of stress hormones, inflammation, and potential sensor inaccuracies can combine to create a dangerous situation if not managed vigilantly. By understanding how infections affect glucose metabolism, recognizing the specific vulnerabilities of lens technology, and implementing proactive sick-day strategies, patients can better navigate these periods of illness. Maintaining open communication with healthcare providers, adhering to preventive care routines, and respecting the limits of the device during acute sickness are essential steps toward safer, more stable diabetes management.

For further reading, the Mayo Clinic offers guidance on diabetes and infections, and the American Diabetes Association updates sick-day rules regularly based on emerging evidence. Diabetic lens users are encouraged to discuss device-specific sick-day protocols with their eye care specialist and endocrinologist as part of their comprehensive diabetes management plan.