Diabetes Sick Day Rules: What to Do When You're Ill and Blood Sugar Spikes

When you have diabetes, a condition where the body struggles to manage blood sugar levels. Also known as hyperglycemia, it requires careful daily attention—but when you're sick, even small changes can throw everything off. Illness triggers stress hormones that raise blood sugar, no matter how well you’ve been managing before. That’s why diabetes sick day rules, a set of proven actions to follow when you’re unwell aren’t optional—they’re life-saving.

These rules aren’t about perfection. They’re about staying ahead of danger. When you have a cold, flu, or infection, your body doesn’t need less insulin—it often needs more. Stopping your insulin because you’re not eating can lead to diabetic ketoacidosis, a life-threatening buildup of acids in the blood. You still need to check your blood sugar every 2 to 4 hours, even if you’re too sick to eat. Drink fluids to avoid dehydration, and test for ketones if your blood sugar stays above 240 mg/dL. Many people don’t realize that nausea or vomiting with high blood sugar isn’t just a stomach bug—it could be ketoacidosis in progress.

Insulin adjustments aren’t guesswork. If you use insulin, you need to know how much to increase based on your blood sugar readings and whether ketones are present. Your doctor should have given you a sick day plan, but if you haven’t got one, now’s the time to ask. Don’t wait until you’re too weak to call. Keep fast-acting carbs on hand—not to treat high blood sugar, but to prevent lows if you’re vomiting or can’t eat. And remember: if you’re confused, breathing fast, or smell fruity on your breath, go to the ER. These aren’t normal symptoms. They’re red flags.

Below, you’ll find real-world advice from people who’ve been through this—how to track your numbers, what to stock in your medicine cabinet, when to call your provider, and how to avoid the most common mistakes that land people in the hospital. These aren’t theory-based tips. They’re what works when you’re too sick to think straight but still need to stay alive.