Sick-Day Guidance for Diabetes: General Principles

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Being sick — even with something as ordinary as a cold or stomach bug — can affect blood sugar in ways that catch people off guard. Illness often raises blood sugar due to stress hormones, even when appetite and food intake drop.

Why illness changes the picture

The body's stress response to infection or illness releases hormones that can raise blood sugar, independent of what you're eating. This means blood sugar can run high during a stomach bug even if you're barely eating — the opposite of what many people expect.

General sick-day principles

• Test blood sugar more frequently than usual — many care teams recommend every 2-4 hours during illness
• Continue taking prescribed medications unless your doctor has told you otherwise; illness is not typically a reason to stop diabetes medication on your own
• Stay hydrated with sugar-free fluids if blood sugar is high, or with small amounts of regular fluids if you're unable to eat and blood sugar is trending low
• Keep a log of readings, temperature, and symptoms to share with your doctor if needed

Warning signs that need urgent medical attention

Seek emergency care for persistent vomiting, inability to keep fluids down, signs of dehydration, very high or very low blood sugar that isn't responding to your usual routine, or symptoms of diabetic ketoacidosis such as fruity-smelling breath, rapid breathing, or confusion. These are medical emergencies, not situations to manage alone.

Have a written plan ready

Many care teams provide a written sick-day plan in advance — it's worth asking for one before you need it, since decision-making is harder when you're unwell. Track any readings with our unit converter if your devices report in different units.

Ketone testing during illness

For people with type 1 diabetes especially, checking urine or blood ketones during illness — particularly if blood sugar is high — is often part of a sick-day plan, since illness combined with high blood sugar and insulin needs can raise the risk of diabetic ketoacidosis. Many care teams provide specific ketone-testing guidance as part of a written sick-day plan; ask for one if you haven't received it.

When to call your doctor versus go to the ER

A general rule many care teams suggest: call your doctor's office for guidance if symptoms are manageable but you're unsure what to do, and go to an emergency room or call emergency services for severe symptoms — persistent vomiting, confusion, difficulty breathing, or inability to keep fluids down. When in doubt, particularly with children or anyone unable to communicate clearly, err toward emergency care.

Sources

NIDDK: Diabetic Ketoacidosis · American Diabetes Association: Sick Days