Sick Days: Fever, Infection and Your Sugar
Reviewed by CDE Mehandi Sharma · Updated
When you are ill, your body releases hormones to fight the illness, and those hormones push your blood sugar up. This happens even if you are eating almost nothing, which is why illness catches people out — and why a run of unexplained high readings is worth checking for infection.
The most important rule: keep taking your insulin and diabetes tablets as usual, even if you are not eating normally. Stopping them because you have skipped meals is the common and dangerous mistake.
What to do while you are ill
- Check your blood sugar every four hours and write the results down.
- Test for ketones, especially if your reading is 240 mg/dL or above.
- Drink plenty of water. If you cannot keep fluids down, take small sips or ice chips every 15 minutes.
- If you cannot eat meals, aim for around 50 grams of carbohydrate every four hours — something simple like juice or thin khichdi.
Get emergency help if you have trouble breathing, ketones present, cannot keep liquids down for more than four hours, cannot keep food down for a day, are vomiting or have diarrhoea beyond six hours, have a fever over 101°F for a day, or your blood sugar drops below 60 mg/dL.