Being sick raises blood sugar, a phenomenon known as stress hyperglycemia. This is a common and expected response when the body fights off an illness like a cold, the flu, or an infection. While this reaction is a natural defense mechanism to provide energy, it results in elevated glucose levels that can be dangerous for people with diabetes. Managing blood sugar during sickness is a proactive step to prevent serious complications from sustained high glucose.
How Illness Triggers Blood Sugar Spikes
Illness triggers a physiological cascade designed to mobilize energy for the immune system, leading directly to higher glucose levels. When the body detects a threat, such as a virus or bacteria, it initiates a stress response involving the release of specific counter-regulatory hormones. These hormones include cortisol, adrenaline (epinephrine), and glucagon, which all work against the effects of insulin.
Adrenaline and glucagon primarily signal the liver to increase glucose production through processes like gluconeogenesis and glycogenolysis. This floods the bloodstream with extra sugar, providing immediate fuel for immune cells and the brain. Simultaneously, hormones like cortisol and growth hormone cause temporary insulin resistance in the body’s muscles and fat cells.
This resistance means the body’s cells do not respond effectively to available insulin, preventing glucose from moving out of the blood and into the cells. Cytokines, small proteins produced by the immune system, further contribute to this reduced insulin sensitivity. The net effect is a significant and rapid rise in blood sugar, even if a person is eating less food than usual.
Essential Sick Day Management
Monitoring
Managing diabetes during illness requires diligent steps to counteract the body’s stress response and prevent blood sugar from becoming dangerously high or low. Increase the frequency of blood glucose monitoring, checking levels at least every two to four hours, even overnight. This surveillance allows for timely adjustments to medication, which is important since high blood sugar can signal a worsening infection.
Hydration
Maintaining hydration is a primary concern, as high blood sugar increases urination and leads to dehydration. Consume at least one cup (250 mL) of fluid every hour while awake. If blood sugar levels are high (e.g., above 240 mg/dL), choose fluids without sugar, such as water or sugar-free sports drinks.
Nutrition
Nutrition must be addressed, even with a poor appetite, to prevent hypoglycemia, especially for people taking insulin. If regular meals cannot be tolerated, consume about 15 grams of easily digestible carbohydrates every hour. Examples include broth, crackers, or small amounts of juice, though non-carbohydrate fluids are preferred if blood sugar is already elevated.
Medication Adjustments
Medication adjustments are common, and insulin users often require extra short-acting insulin to correct for illness-induced hyperglycemia. Long-acting (basal) insulin doses must never be stopped, as this can quickly lead to Diabetic Ketoacidosis (DKA). For those on oral medications, certain drugs like Metformin and SGLT-2 inhibitors may need to be temporarily stopped if there is severe vomiting, diarrhea, or dehydration.
Ketone Testing
Testing for ketones is necessary during illness, particularly for those with Type 1 diabetes or anyone with blood glucose consistently above 240 mg/dL. Ketones are a byproduct of fat breakdown that accumulate when the body lacks enough insulin to use glucose. The presence of ketones indicates an increased risk of developing DKA and requires immediate action and communication with a healthcare provider.
Warning Signs Requiring Immediate Medical Attention
A non-severe illness, such as a common cold, can often be managed at home, but certain warning signs indicate a medical emergency requiring professional care. Seek immediate medical attention if you experience any of the following:
- Persistent vomiting or diarrhea, especially if fluids cannot be kept down for more than four to six hours, which can quickly lead to severe dehydration.
- Sustained, high blood sugar levels that do not respond to corrective insulin doses. If blood glucose remains above 300 mg/dL on two consecutive tests, seek medical help.
- The presence of moderate to high ketones in the urine or blood, particularly when accompanied by symptoms like nausea, abdominal pain, or fruity-smelling breath (indicators of DKA).
- Changes in mental status, such as confusion, extreme drowsiness, or severe lethargy, which can signal DKA or Hyperosmolar Hyperglycemic State (HHS).
- Difficulty breathing or a high fever that lasts longer than 24 hours.