Understanding the Risks of Illness With Diabetes

When you have diabetes, even a common cold, a bout of flu, or a stomach virus can create a cascade of metabolic challenges. Illness triggers the release of stress hormones such as cortisol and adrenaline, which counter the action of insulin and cause the liver to release stored glucose. This response, while protective for people without diabetes, can send blood sugar levels dangerously high for those with the condition. Conversely, if you are taking certain glucose-lowering medications and are unable to eat due to nausea, you risk dropping into hypoglycemia. Managing diabetes when you are unwell requires a well-thought-out sick-day plan that you discuss with your healthcare team before you actually get sick.

According to the Centers for Disease Control and Prevention (CDC), people with diabetes are more likely to have complications from common illnesses like influenza and pneumonia. High blood sugar impairs the function of neutrophils and other immune cells, making it harder for your body to fight off the underlying infection. The key is to stay proactive, monitor frequently, and adjust your care as needed. The risk of hospitalization for influenza is significantly higher in the diabetic population, underscoring the need for a robust prevention and management strategy.

Why Blood Sugar Fluctuates During Illness

Several mechanisms can send your glucose in either direction when you are sick. Understanding the reasons helps you anticipate changes and respond appropriately without panic.

Stress Hormones and Counter-Regulatory Responses

Your body sees illness as a stressor. Hormones such as catecholamines (adrenaline and noradrenaline) and cortisol are released to help you fight the infection. These hormones oppose the action of insulin and promote gluconeogenesis — the production of new glucose from non-carbohydrate sources in the liver. For people with type 1 diabetes or insulin-deficient type 2 diabetes, this can lead to hyperglycemia that is difficult to control without additional insulin. Even people with well-controlled type 2 diabetes may see elevated levels that persist until the underlying infection resolves.

The Impact of Infection on Insulin Resistance

When your body is fighting an infection, it releases inflammatory cytokines. These chemical messengers promote a state of profound insulin resistance in the liver, fat, and muscle tissue. This means your usual dose of insulin or oral medication may not be as effective, often requiring higher, temporary doses to achieve the same glucose-lowering effect. This resistance is directly proportional to the severity of the illness; a mild cold may cause a slight bump, while a serious bacterial infection can double or triple your insulin needs.

Reduced Food and Fluid Intake

On the other hand, if you are vomiting, have diarrhea, or simply lose your appetite, you may not be taking in enough carbohydrates. If you are using insulin or sulfonylureas, this can cause hypoglycemia. The risk is especially high if you continue your usual medication doses while eating much less than normal. Balancing the risk of hyperglycemia from stress hormones with the risk of hypoglycemia from reduced intake is the central challenge of sick-day management. This balancing act is why frequent monitoring is non-negotiable.

Dehydration and Electrolyte Imbalance

High blood sugar causes osmotic diuresis — increased urination — which can lead to dehydration. Illness with fever, vomiting, or diarrhea compounds fluid losses. Dehydration further elevates blood glucose because the concentration of glucose in the blood increases as plasma volume decreases. Additionally, electrolyte imbalances, particularly in potassium and sodium, can affect heart function and kidney performance. Maintaining hydration is a critical part of any sick-day strategy, as severe dehydration can progress to hyperosmolar hyperglycemic state (HHS), a life-threatening emergency distinct from diabetic ketoacidosis.

Creating a Sick-Day Plan With Your Healthcare Provider

Every person with diabetes should have a written sick-day plan that is reviewed and updated at least once a year. The plan should cover:

  • How often to check blood glucose — typically every 2–4 hours, and more often if levels are out of range.
  • When to test for ketones — especially for those with type 1 diabetes or insulin-dependent type 2 diabetes.
  • Medication adjustments — including specific instructions for insulin (both basal and bolus) and for oral agents (many of which may need to be temporarily stopped).
  • When to call your healthcare team — clear thresholds for blood glucose and ketone levels, and what symptoms warrant emergency attention.
  • What to eat and drink — a “sick-day menu” with options that provide about 15 grams of carbohydrate per hour if regular meals cannot be tolerated.

The American Diabetes Association emphasizes that a proactive plan reduces the risk of hospitalization and diabetic ketoacidosis (DKA). You should discuss whether your medications need to be adjusted.

Assembling Your Sick-Day Kit

Being prepared means having all the necessary supplies in one place so you don’t have to search for them when you feel terrible. Your sick-day kit should include:

  • Glucose meter with extra batteries, test strips, and lancets
  • Urine ketone strips or a blood ketone meter
  • Fast-acting glucose (glucose tablets, glucose gel, or juice boxes)
  • Easy-to-digest carbohydrates (saltines, pretzels, applesauce, plain toast)
  • Thermometer and fever-reducing medication (acetaminophen or ibuprofen)
  • Electrolyte replacement fluids (Pedialyte, diluted sports drinks)
  • Anti-nausea medication (if previously prescribed by your doctor)
  • Emergency contact numbers for your care team and family

Monitoring Blood Sugar and Ketones

During illness, checking your blood glucose more often than usual is non-negotiable. Aim for every 2 to 4 hours, and always before making any medication adjustments. Keep a log that includes glucose numbers, medication doses, food and fluid intake, and any symptoms. This record is invaluable when you talk to your healthcare provider.

For people with type 1 diabetes, and for some with type 2 diabetes who take insulin, ketone testing is essential. Ketones are acidic byproducts of fat breakdown that accumulate when there is not enough insulin to push glucose into cells. High ketones, combined with high blood glucose, lead to DKA — a life-threatening emergency. Use urine ketone strips or a blood ketone meter. Check for ketones if your blood glucose is above 240–250 mg/dL (13.3–13.9 mmol/L), or if you have nausea, vomiting, or abdominal pain.

If you have moderate to large ketones, do not exercise. Instead, rest, drink plenty of water, and follow your sick-day plan. Contact your healthcare team immediately if ketones remain high or if you cannot keep fluids down. The Mayo Clinic notes that DKA requires emergency treatment, often with intravenous fluids and insulin.

A Note on Continuous Glucose Monitors (CGM)

If you use a CGM, keep in mind that accuracy can be affected by dehydration or rapid changes in glucose levels. CGM sensors rely on interstitial fluid, which can lag behind blood glucose during times of rapid flux. Always confirm CGM readings with a fingerstick blood glucose test before making critical treatment decisions, especially if you feel the number does not match your symptoms.

Medication Management During Illness

Never stop taking your diabetes medications without consulting your provider, but be aware that some medications need to be paused temporarily. Having a clear plan for each medication class is vital.

Insulin Therapy Adjustments

Most insulin-treated patients will need to increase their insulin doses during illness because of the hyperglycemic effects of stress hormones. Basal insulin (long-acting) should almost never be omitted — even if you are not eating — because it prevents the breakdown of fat into ketones, thus preventing diabetic ketoacidosis. You may need a supplemental “correction” dose of rapid-acting insulin more frequently. Work out a dosing algorithm with your provider in advance. For example, if your correction factor is 1 unit for every 50 mg/dL above a target of 150, and your blood sugar is 350, a corrective dose of 4 units might be warranted, but your specific plan may differ. For those on insulin pumps, having a backup plan for site changes and temporary basal rates is critical, as infusion set failures during illness can lead to rapid DKA onset.

Oral Medications and Non-Insulin Injectables

Metformin can sometimes cause gastrointestinal upset, so it may be temporarily stopped if you have vomiting or diarrhea. However, it does not cause hypoglycemia by itself, so missing a dose is usually safe. Sulfonylureas (like glipizide, glimepiride) can cause hypoglycemia if you are eating less — your provider may advise skipping them until you are eating normally again. SGLT2 inhibitors (such as empagliflozin, dapagliflozin) should be stopped during acute illness because they increase the risk of a rare but serious condition called euglycemic diabetic ketoacidosis, where blood sugar can be normal but ketones are dangerously high. GLP-1 receptor agonists (liraglutide, semaglutide) can cause nausea and dehydration, so they may be temporarily held as well. Newer dual agonists like tirzepatide also delay gastric emptying, which can complicate fluid intake during illness. Always follow your specific sick-day instructions from your endocrinologist or diabetes educator.

Nutrition and Hydration Strategies

When you are unwell, eating a balanced meal might be the last thing on your mind. Yet getting some carbohydrates and plenty of fluids is vital for maintaining glucose stability and avoiding dehydration.

The "15-Gram" Approach

If you cannot eat a normal meal, aim to consume about 15 grams of carbohydrate every hour. Spread this out to avoid large glucose spikes. Good choices include:

  • ½ cup of regular gelatin (not sugar-free)
  • 1 cup of Gatorade or a similar sports drink
  • 1 cup of milk
  • 3–4 saltine crackers
  • ½ cup of applesauce

If you are nauseated, try clear liquids first: broth, flat ginger ale, or clear fruit juice (limit to ¼ cup at a time to avoid high sugar). Once you can tolerate solids, move to bland, easy-to-digest foods like the BRAT diet — Bananas, Rice, Applesauce, Toast. These provide steady carbohydrates and are gentle on the stomach. Avoid high-fat foods that can delay gastric emptying and worsen nausea.

Hydration and Electrolyte Balance

Drink at least 8 ounces (240 mL) of fluid every hour while awake. Water is best, but if you have vomiting or diarrhea, include fluids with electrolytes — such as low-sugar sports drinks (diluted 50:50 with water), clear broth, or oral rehydration solutions (like Pedialyte). Avoid fruit juices and regular sodas, as they contain concentrated sugar that can spike glucose levels further. If you have heart failure or kidney disease, discuss fluid targets with your provider because excessive intake can be harmful. A good rule of thumb is to sip fluids constantly rather than gulping large volumes, which can trigger vomiting.

When to Seek Medical Help Immediately

Not all illnesses can be managed at home. Know the warning signs that require prompt medical attention:

  • Persistent vomiting or diarrhea for more than 6 hours
  • Inability to keep down any food or fluids
  • Blood glucose > 300 mg/dL (16.7 mmol/L) after two correction doses
  • Moderate to large urine ketones or blood ketones > 1.0 mmol/L
  • Severe symptoms such as confusion, fruity breath, rapid breathing, or difficulty waking up
  • High fever (over 101.5°F / 38.6°C) that does not respond to acetaminophen
  • Shortness of breath or chest pain

Do not delay calling 911 or going to the emergency room. Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are medical emergencies that can progress quickly, especially in older adults or those with other chronic conditions. HHS often presents with extreme dehydration and confusion, while DKA is characterized by rapid breathing and a fruity odor on the breath. Both require immediate hospital intervention.

Rest, Hygiene, and Prevention

While managing your diabetes actively, give your body the rest it needs to fight the infection. Sleep helps regulate immune responses and also reduces stress hormone levels, which indirectly helps stabilize blood sugar. Pushing through illness to work or handle daily chores will likely prolong the infection and make glucose management far more difficult.

Maintain strict hygiene: wash your hands frequently, avoid touching your face, and isolate from other household members if possible to avoid spreading or picking up more infections. Keep surfaces clean and sanitize your blood glucose meter and lancet device. Dispose of used lancets and test strips properly to prevent contamination.

Prevention is the best protection. The CDC recommends annual flu shots for everyone with diabetes, along with pneumococcal vaccination (pneumonia vaccine) and, if eligible, the RSV vaccine and COVID-19 boosters. Staying up to date with immunizations reduces your risk of severe illness that could destabilize your diabetes control.

Communicating With Your Support Network

Tell family members, close friends, and coworkers about your sick-day plan. Make sure someone knows where you keep your medications, glucose meter, and emergency contact numbers. If you live alone, check in with someone at least twice a day when you are ill. Consider wearing a medical ID bracelet or necklace that indicates you have diabetes, especially if you take insulin or medications that can cause severe hypoglycemia. You can also set up a medical ID on your smartphone lock screen. A simple piece of identification can guide first responders to treat you appropriately if you are found unable to communicate.

Managing an acute illness on top of the daily demands of diabetes management can feel overwhelming. Anxiety about fluctuating numbers, the worry of DKA, and the physical exhaustion of fighting an infection can take a significant emotional toll. It is important to give yourself grace during these periods. You do not need to have perfect blood sugar numbers while you are sick. The goal shifts from tight control to damage control: staying hydrated, taking your medications as directed, and monitoring for danger signs. Rest is medicine. Do not be afraid to ask for help from family or friends to manage meals or pick up prescriptions. Mental stress also raises blood sugar, so accepting help and lowering your expectations for perfection can actually improve your physical health outcomes.

Conclusion: Staying Prepared Reduces Stress

The unpredictability of illness is one of the hardest parts of living with diabetes. But with a solid sick-day plan, regular monitoring, and prompt adjustments to medications and nutrition, you can navigate most minor illnesses at home without landing in the hospital. Prepare your plan now, keep a sick-day kit stocked with glucose strips, ketone test supplies, and the right foods, and review it with your diabetes care team every year. Being proactive means you spend less time worrying and more time recovering.

Every bout of illness is also a learning opportunity. After you recover, review what happened with your healthcare team. What worked well? What would you change? Refining your sick-day plan ensures you are even more prepared for the next time. The ultimate goal is not just to survive being sick, but to manage your diabetes effectively so you can recover smoothly and avoid the serious complications that arise when diabetes management takes a backseat during illness. Remember: when in doubt, check your blood sugar, check for ketones, and call your healthcare provider. Your health and safety come first.