When you have diabetes and become ill, even a common cold or stomach bug can disrupt your blood sugar control in ways that feel unpredictable. Illness triggers the release of stress hormones like cortisol and adrenaline, which raise blood glucose levels, while reduced appetite, vomiting, or diarrhea can cause dangerously low blood sugar. Without careful adjustments to your treatment plan, the risk of diabetic ketoacidosis (DKA) in type 1 diabetes or hyperosmolar hyperglycemic state (HHS) in type 2 diabetes increases significantly. Having a solid sick-day management strategy in place before you get sick can make all the difference. This guide provides a comprehensive, actionable approach to adjusting your diabetes treatment plan when you are under the weather, so you can stay safe and recover faster.

Why Illness Affects Your Blood Sugar

Understanding the biological mechanisms at play helps you anticipate the changes in your glucose levels. When your body fights an infection—whether viral, bacterial, or fungal—it produces stress hormones and inflammatory cytokines. These substances promote insulin resistance, meaning your cells do not respond to insulin as effectively as they normally do. As a result, the liver releases stored glucose into the bloodstream, even if you have not eaten. This can lead to persistent hyperglycemia.

However, the picture is not always one-sided. If the illness causes nausea, vomiting, diarrhea, or loss of appetite, you may not be consuming enough carbohydrates to keep up with your body’s energy demands. In that scenario, blood sugar can drop, especially if you continue taking your usual doses of insulin or certain oral medications like sulfonylureas. The key is to monitor closely and adjust based on real-time data rather than assumptions.

Monitoring Blood Sugar Levels More Frequently

During illness, your usual monitoring schedule is no longer sufficient. You need to check your blood glucose every two to four hours around the clock. If you use a continuous glucose monitor (CGM), ensure the sensor is well calibrated and that you are responding to alerts promptly. For those on insulin pumps, be aware that infusion sites can become less effective during illness due to changes in skin perfusion or inflammation—consider rotating sites more frequently.

Keep a detailed log of every reading along with notes about symptoms, medication doses, food intake, and fluid consumption. This record becomes invaluable when you contact your healthcare provider, as it helps them assess whether you need a dose adjustment or more urgent intervention. If you experience vomiting or diarrhea, check for ketones as well—urine or blood ketone testing should be performed every four hours when blood glucose exceeds 250 mg/dL (13.9 mmol/L) or when you are unable to eat normally.

Key Numbers to Watch

  • Blood glucose above 240 mg/dL (13.3 mmol/L): Test for ketones immediately, and recheck every four hours until readings normalize.
  • Blood glucose below 70 mg/dL (3.9 mmol/L): Treat hypoglycemia with 15 grams of fast-acting carbohydrate, then recheck in 15 minutes.
  • Persistent hyperglycemia despite correction doses: This may indicate the need for additional insulin or medical evaluation.

Adjusting Your Medications Safely

Never stop taking your diabetes medications during illness unless specifically instructed by your healthcare team. However, the doses may need to change. The adjustments depend on the type of diabetes, the medications you use, and the nature of your illness.

Insulin Adjustments

For people with type 1 diabetes, the general rule is never to omit basal insulin, even if you are not eating. Basal insulin provides background coverage to prevent ketone production. Missing a dose can rapidly lead to DKA. Bolus (mealtime) insulin may need to be reduced if you are eating less, but you may also need extra correction boluses if your blood sugar is high. Many experts recommend setting temporary basal rates if you use an insulin pump—either increasing by 20% to 50% for hyperglycemia or decreasing if vomiting causes low sugars. Consult your endocrinologist for a personalized sick-day basal adjustment plan.

For people with type 2 diabetes who use insulin, similar principles apply. If you are not eating, you may still need a lower dose of long-acting insulin. Rapid-acting insulin should be dosed based on blood sugar readings and planned carbohydrate intake. When in doubt, take a conservative approach and check more frequently.

Oral Medications

Several classes of oral diabetes drugs require special consideration during illness:

  • Metformin: Generally safe during mild illness, but if you develop vomiting, diarrhea, or dehydration, metformin should be temporarily stopped due to the risk of lactic acidosis. Restart when you can eat and drink normally.
  • Sulfonylureas (e.g., glipizide, glyburide): These drugs can cause hypoglycemia if you are not eating. You may need to reduce the dose or skip it until your appetite returns. Monitor closely.
  • SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin): These increase the risk of euglycemic DKA (ketones without very high blood sugar). Many clinicians recommend holding these medications during any illness that limits oral intake. Check with your doctor.
  • DPP-4 inhibitors and GLP-1 agonists: These are generally lower risk but may need to be paused if you cannot eat or if nausea is severe. GLP-1 agonists can worsen gastrointestinal symptoms, so discuss timing with your provider.

Important: Always contact your healthcare provider before making significant changes to your medication regimen. Sick-day dosing guidelines vary greatly from person to person.

Managing Hydration and Nutrition

Staying hydrated is arguably the most critical non-medication intervention during illness. Dehydration concentrates blood glucose and increases the risk of DKA and HHS. Aim to drink 8 to 12 ounces of fluid every hour while awake. Water is excellent, but you may also need fluids that contain electrolytes and some carbohydrates if you are losing them through vomiting or diarrhea.

Sip clear liquids regularly. If you cannot tolerate solid food, try gelatin, popsicles, broth, or diluted fruit juice. Avoid sugary sodas, regular fruit juice in large amounts, and any drink containing high-fructose corn syrup unless you are treating hypoglycemia. Unsweetened tea, sugar-free electrolyte drinks, or broth are good choices.

When you do have an appetite, choose foods that are gentle on the stomach and provide consistent carbohydrates. The BRAT diet (bananas, rice, applesauce, toast) is a classic starting point. Other options include crackers, oatmeal, plain yogurt, or boiled potatoes. Try to eat small amounts every hour or two rather than large meals. If you are on a fixed insulin schedule, you may need to match your carbohydrate intake to your doses—plan ahead.

Carbohydrate Guidelines During Illness

  • If you can eat normally: Stick to your usual carbohydrate goals but test more often.
  • If you have a reduced appetite: Aim for 15 to 30 grams of carbohydrate every two to three hours to prevent hypoglycemia and maintain energy.
  • If you cannot keep anything down: Focus on hydration and ketone monitoring. Contact your healthcare provider if you cannot eat for more than six hours.

Building a Sick-Day Action Plan

Preparation is the best defense. Work with your diabetes educator or endocrinologist to create a written sick-day plan that you can post on your refrigerator or save in a notes app. Your plan should include:

  1. Supplies: Extra test strips, glucose tabs or gel, ketone test strips, glucagon kit (if you use insulin), and backup insulin supplies.
  2. Contact information: Your doctor’s office, on-call endocrinologist, and a trusted family member or friend who can help.
  3. Dosing guidelines: How to adjust basal and bolus insulin or oral medications based on blood sugar and ketone thresholds.
  4. Fluid and food plan: What to drink and eat, and when to switch from solids to liquids.
  5. When to seek emergency care: Clearly defined criteria (see below).

Review this plan at least once a year and update it if your medications or health status change. If you travel frequently, keep a copy with you.

Recognizing and Treating Hyperglycemia and Hypoglycemia

Illness can swing blood sugar in either direction, often within hours. Knowing the symptoms and having a rapid response strategy is essential.

Hyperglycemia (High Blood Sugar)

Symptoms include increased thirst, frequent urination, dry mouth, blurred vision, fatigue, and weight loss. If your blood sugar is elevated, take the following steps:

  • Check for urine or blood ketones. If moderate or large ketones are present (or if blood beta-hydroxybutyrate is >0.6 mmol/L), contact your healthcare provider immediately.
  • Drink plenty of water to help flush excess glucose through the kidneys.
  • Administer a correction dose of rapid-acting insulin according to your sick-day plan. Do not exceed recommended doses without medical advice.
  • If you are using an insulin pump, check the infusion site for occlusion or infection. Replace the set if in doubt.
  • Rest and avoid strenuous activity, which can further stress the body.

Hypoglycemia (Low Blood Sugar)

Symptoms include shakiness, sweating, confusion, irritability, rapid heartbeat, and hunger. During illness, hypoglycemia can occur if you have missed meals, taken too much insulin/sulfonylurea, or experienced vomiting. Treat immediately:

  • Consume 15 grams of fast-acting carbohydrate: three to four glucose tablets, half a cup of fruit juice, or one tablespoon of sugar or honey.
  • Recheck blood sugar after 15 minutes. If still below 70 mg/dL, repeat the treatment.
  • Once blood sugar is above 70 and your next meal is more than an hour away, eat a small snack containing protein and carbs (e.g., half a sandwich, crackers with peanut butter).
  • If you are unconscious or unable to swallow, administer glucagon if available and call 911 immediately.

When to Seek Medical Help

While many sick days can be managed at home, certain red flags require prompt professional attention. Do not hesitate to call your doctor or go to the emergency department if you experience any of the following:

  • Blood glucose persistently above 250 mg/dL despite correction doses, especially if accompanied by moderate-to-large ketones.
  • Inability to keep down fluids or medications for more than six hours due to vomiting.
  • Severe diarrhea lasting more than 24 hours.
  • Symptoms of DKA: fruity-smelling breath, rapid deep breathing, abdominal pain, confusion, or extreme lethargy.
  • Symptoms of HHS: extreme thirst, dry mouth, warm dry skin, fever, drowsiness, or neurological changes.
  • Any illness that lasts longer than 48 hours without improvement.
  • Fever above 101°F (38.3°C) that does not respond to over-the-counter fever reducers.

Remember, DKA and HHS are life-threatening emergencies requiring intravenous fluids and insulin in a hospital setting. It is far better to err on the side of caution and be evaluated than to wait until complications become severe.

Consulting Your Healthcare Team

Your endocrinologist, primary care provider, certified diabetes educator, and pharmacist are valuable allies during illness. Ideally, you should have a sick-day protocol reviewed with them before you get sick. If you feel uncertain about any aspect of your management, call the office. Many clinics offer after-hours triage lines specifically for diabetes patients.

Be prepared to share your log of blood sugar readings, ketone results, medication doses, symptoms, and temperature. This information helps the clinician determine whether you can stay at home or need to come in. It also enables them to give precise dosing adjustments over the phone.

If you do not have a sick-day plan yet, schedule an appointment soon to develop one. Organizations like the American Diabetes Association and the CDC provide general guidelines, but your personal plan should be tailored to your specific medications, lifestyle, and complications.

Additional Considerations: Stress, Infection, and Monitoring Technology

Psychological stress from being sick can further elevate blood glucose. Practice relaxation techniques like deep breathing, listening to calming music, or gentle stretching if you are able. Adequate sleep is also crucial—cortisol levels rise with sleep deprivation, worsening hyperglycemia.

Infection itself can cause a systemic inflammatory response that makes insulin resistance profound. Even a mild respiratory infection can double your daily insulin needs in some cases. Monitor trends proactively rather than waiting for extreme values.

Modern diabetes technology can simplify sick-day management. Continuous glucose monitors (CGMs) provide real-time trends and alarms for high and low extremes. Set your high alarm to 200 mg/dL during illness to catch problems early. Insulin pumps with automated insulin delivery systems may suspend insulin delivery in response to low glucose, but you must still be vigilant about checking ketones if the pump is off. Talk to your pump manufacturer or provider about how to use temporary basal rates and activity modes effectively.

Putting It All Together: A Sample Sick-Day Routine

Here is a step-by-step example of what a typical sick day might look like for someone with diabetes:

  1. Morning: Wake up, check blood sugar and ketones. Record both. If ketones are positive, hydrate and plan to test more frequently.
  2. Medication: Take basal insulin as usual. Hold off on oral meds if vomiting is present. Call doctor if uncertain.
  3. Breakfast: Sip clear fluids. If able, eat a few saltine crackers with a small amount of peanut butter. Check blood sugar two hours later.
  4. Midday: Recheck blood sugar and ketones. If elevated and ketones persist, administer extra rapid-acting insulin per your sick-day plan. Drink 8 oz of electrolyte solution.
  5. Afternoon: Continue fluid intake. If nausea improves, try a small bowl of soup or applesauce. Monitor blood sugar before and after.
  6. Evening: Check ketones again. If blood sugar remains above 250 with moderate ketones, contact on-call endocrinologist. Consider going to urgent care if symptoms worsen.
  7. Bedtime: Set alarm to check blood sugar at 2 AM. Have glucagon and fast-acting glucose available.

Document everything so you can review the next day with your healthcare team.

Final Thoughts: Be Prepared, Stay Safe

Having diabetes does not mean that a simple cold must become a crisis. With careful monitoring, appropriate medication adjustments, and a clear action plan, you can manage most illnesses at home. The most important steps are to test frequently, stay hydrated, never skip basal insulin, and contact your healthcare provider early if something feels off. By taking ownership of your sick-day strategy, you protect yourself from serious complications and pave the way for a smoother recovery.

For more detailed information, refer to Mayo Clinic's guide on diabetic emergencies and the Joslin Diabetes Center sick-day guidelines. Stay well and stay informed.