Being sick often causes an elevation in blood sugar, known as stress hyperglycemia, which occurs even in individuals without a diabetes diagnosis. This increase is a natural, protective response by the body to injury or infection, but it presents a significant challenge for people managing diabetes. Even a minor illness can destabilize glucose control, potentially leading to dangerously high blood sugar levels. Understanding the body’s reaction to sickness is the first step in effectively managing glucose levels during periods of poor health.
The Physiological Response to Illness
When the body faces an illness, infection, or physical injury, it activates a stress response, often referred to as the “fight or flight” mechanism. This response is mediated by the release of powerful stress hormones, most notably cortisol and adrenaline (epinephrine). These hormones are designed to mobilize energy reserves to help the body fight the threat and fuel the immune system.
Cortisol and adrenaline signal the liver to increase its production and release of stored glucose, a process called gluconeogenesis. This surge of glucose provides immediate energy for the immune system and the brain. Simultaneously, these stress hormones cause a temporary state of insulin resistance throughout the body.
Insulin resistance means that the body’s cells become less responsive to insulin, making it more difficult for the hormone to move glucose out of the bloodstream and into the cells for energy. This dual action—increased glucose production and reduced glucose uptake—results in elevated blood sugar levels. For individuals with diabetes, whose insulin production or sensitivity is already compromised, this stress response necessitates a significant adjustment in management.
Specific Illnesses That Affect Blood Sugar
Nearly any physical stressor that triggers the body’s acute phase response can lead to a rise in blood sugar levels. The severity of the illness is generally proportional to the magnitude of the glucose elevation. Common infections are frequent culprits, including influenza, the common cold, and pneumonia.
Bacterial infections, such as urinary tract infections (UTIs) or skin abscesses, are especially likely to cause significant hyperglycemia due to the robust immune response they provoke. Illnesses involving the digestive system, such as viral gastroenteritis with vomiting or diarrhea, can complicate blood sugar control by affecting fluid balance and nutrient absorption. Even procedures like post-surgical recovery and the use of certain medications, notably corticosteroids, can introduce enough stress to cause a substantial and sustained blood sugar rise.
Practical Sick Day Management
Effective sick day management focuses on consistent monitoring, maintaining hydration, and making appropriate adjustments to diabetes medication. Individuals with diabetes should check blood sugar levels much more frequently than usual, typically every two to four hours, even overnight. This frequent testing allows for timely recognition of dangerous trends because blood sugar can change rapidly during illness.
Maintaining adequate fluid intake is important to prevent dehydration, which can worsen hyperglycemia and increase the risk of complications. Aim to consume small, frequent sips of fluid, such as 4 to 6 ounces every half hour, even if nausea or vomiting is present. If blood sugar levels are high (e.g., above 200 mg/dL), sugar-free fluids are recommended. If levels drop below a target range, carbohydrate-containing fluids like regular soda or juice may be necessary to prevent hypoglycemia.
Never stop taking insulin during an illness, as the body’s demand for insulin often increases due to stress-induced insulin resistance. Patients taking insulin will likely need to follow a sick day plan developed with their healthcare team, which often involves increasing the dose of rapid-acting insulin to correct high blood sugar. Patients on certain oral medications, particularly SGLT2 inhibitors and metformin, may need to temporarily stop these drugs, as advised by a doctor, to avoid specific complications.
Ketone monitoring is a necessary part of sick day management for people with Type 1 diabetes and should be performed every four hours when ill. Ketones are byproducts of fat breakdown that occur when the body lacks sufficient insulin to use glucose for energy. If blood sugar is elevated (e.g., above 250 mg/dL) or symptoms like nausea and vomiting are present, ketone testing is mandatory. Moderate or large levels of ketones indicate a severe lack of insulin and require immediate administration of extra rapid-acting insulin and prompt medical consultation.
Recognizing a Blood Sugar Emergency
High blood sugar during illness can progress to emergencies, namely Diabetic Ketoacidosis (DKA) in Type 1 diabetes and Hyperosmolar Hyperglycemic State (HHS) in Type 2 diabetes. DKA develops when a severe insulin deficiency forces the body to burn fat for fuel, producing a buildup of acidic ketones. Warning signs of DKA include persistent vomiting, deep or rapid breathing known as Kussmaul breathing, a fruity odor on the breath, and moderate to large ketones in the blood or urine.
HHS typically develops more slowly and is characterized by extremely high blood sugar levels, dehydration, and hyperosmolarity, often without the presence of high ketones. Symptoms of HHS include extreme thirst, significant confusion, fever, and neurological symptoms like drowsiness or weakness. Both DKA and HHS require immediate medical attention, especially if symptoms like persistent vomiting, difficulty breathing, or an altered mental state are present.