How does illness change blood sugar levels?

Illness typically raises blood sugar levels due to the release of stress hormones like cortisol, adrenaline, and growth hormone that help the body fight infection and recover from disease. According to the American Diabetes Association, any form of physical stress including infections, injuries, or illnesses can cause blood glucose to rise significantly, even in people without diabetes.

The body's stress response during illness triggers several mechanisms that increase blood sugar. When you're sick, your liver releases stored glucose to provide extra energy for healing and immune function. Simultaneously, stress hormones make your cells more resistant to insulin, preventing glucose from entering cells efficiently. This combination creates a perfect storm for elevated blood glucose levels.

Common illnesses that affect blood sugar include respiratory infections like colds and flu, urinary tract infections, dental infections, and gastrointestinal illnesses. Fever is particularly problematic because it increases metabolic demands and stress hormone production. Research published in the Journal of Clinical Medicine shows that even mild infections can raise blood glucose by 50-100 mg/dL above normal levels.

For people with diabetes, illness presents additional challenges. Dehydration from fever or vomiting can concentrate blood glucose further. Reduced appetite may lead to skipping meals, creating unpredictable blood sugar patterns. Certain medications used to treat illness, such as corticosteroids and some cough syrups containing sugar, can also elevate glucose levels.

The duration of elevated blood sugar during illness varies depending on the severity and type of infection. Mild colds may cause temporary spikes lasting 2-3 days, while serious infections like pneumonia can affect blood glucose for weeks. Recovery typically sees gradual normalization as the immune system clears the infection and stress hormone levels decrease.

Healthcare providers recommend more frequent blood glucose monitoring during illness, staying hydrated, and maintaining medication schedules even when appetite is poor. People with diabetes should contact their healthcare team if blood glucose remains above 250 mg/dL for more than 24 hours during illness, as this can lead to dangerous complications like diabetic ketoacidosis.

Understanding how illness affects blood sugar helps both diabetics and non-diabetics recognize when medical attention may be necessary and why glucose management becomes more challenging during recovery periods.

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