When you are sick, blood sugar often rises — even if you are not eating — due to stress hormones. Never stop insulin when ill. Hold SGLT2 inhibitors and possibly metformin. Check blood sugar every 2–4 hours, check ketones if above 250 mg/dL, stay hydrated, and know when to go to the ER.
Illness is one of the most common causes of dangerously high blood sugar in people with diabetes. Infections, fever, vomiting, and physical stress all trigger the release of counter-regulatory hormones (cortisol, glucagon, adrenaline) that raise blood glucose — even if you are not eating. Knowing the sick day rules can prevent a hospitalization.
Rule #1: Never Stop Insulin
This is the most important rule for people with Type 1 diabetes. Insulin is always required — your body cannot make any of its own. Stopping insulin when sick rapidly leads to diabetic ketoacidosis (DKA), a life-threatening emergency. Even if you cannot eat, you still need basal insulin. Your provider may adjust doses, but never stop entirely.
For Type 2 diabetes on insulin: continue basal insulin. Mealtime insulin may be reduced if not eating, but discuss this with your provider in advance.
⚠️ Medications to HOLD When Sick:
• SGLT2 inhibitors (Jardiance, Farxiga, Invokana) — hold immediately when ill; risk of euglycemic DKA
• Metformin — hold if vomiting, severe diarrhea, dehydration, or high fever (lactic acidosis risk in severely ill patients)
• GLP-1 agonists — may worsen nausea; discuss with provider
Continue all other medications unless your provider advises otherwise.
Monitoring Schedule When Sick
- Check blood sugar every 2–4 hours around the clock
- Check ketones (urine or blood) if blood sugar is above 250 mg/dL, especially in Type 1 diabetes
- Keep a sick day log: time, blood sugar, ketone result, symptoms, medications taken, fluids consumed
Hydration
Dehydration worsens blood sugar control and increases DKA risk. Aim for at least 8 oz of fluid per hour:
- If blood sugar is high (>180 mg/dL): water, diet ginger ale, broth, sugar-free popsicles, sugar-free electrolyte drinks
- If blood sugar is low or dropping: regular juice, regular sports drinks, regular ginger ale
- Avoid alcohol
When to Go to the ER
Do not wait — seek emergency care if any of the following occur:
- Blood sugar above 300 mg/dL that is not coming down with correction
- Moderate or large urine ketones, or blood ketones above 1.5 mmol/L
- Vomiting and unable to keep fluids down for 4–6 hours
- Confusion, extreme drowsiness, or difficulty waking up
- Rapid breathing, fruity breath odor (signs of DKA)
- Chest pain, shortness of breath
- Severe abdominal pain
Sick Day Kit — Keep These on Hand
- Blood glucose meter and extra test strips
- Urine ketone strips or blood ketone meter
- Glucose tablets or juice boxes
- Sugar-free clear liquids (broth, electrolyte drinks)
- Thermometer
- Provider's after-hours phone number
- Glucagon kit (Baqsimi, Gvoke, or Zegalogue)
Key Takeaways
- Never stop insulin when sick — illness raises blood sugar even without eating
- Hold SGLT2 inhibitors (Jardiance, Farxiga) immediately when sick — DKA risk
- Hold metformin if vomiting, severely dehydrated, or high fever
- Check blood sugar every 2–4 hours; check ketones if above 250 mg/dL
- Drink at least 8 oz of fluid per hour — sugar-free if blood sugar is high
- Go to the ER for blood sugar above 300 not coming down, moderate ketones, or inability to keep fluids down
- Keep a sick day kit with ketone strips, glucose tablets, glucagon, and provider's number
Our Team Can Help
All five of our providers diagnose and manage endocrine conditions. Book with any member of our team:
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