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

When you have diabetes, a chronic condition where the body can't properly regulate blood sugar. Also known as hyperglycemia, it becomes much more dangerous when you're sick. Illness—whether it's a cold, flu, or infection—triggers stress hormones that raise blood sugar. 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 guessing. They’re about knowing what to check, when to adjust insulin, and when to call for help. For example, if your blood sugar stays above 240 mg/dL for hours, you need to test for ketones. High ketones mean your body is breaking down fat for fuel because it can’t use glucose—this can lead to diabetic ketoacidosis, a life-threatening condition that requires emergency care. Many people don’t realize they’re at risk until they’re already in trouble. That’s why checking ketones with urine strips or a blood meter is part of every sick day plan.

You also need to keep eating, even if you’re nauseous. Skipping meals doesn’t lower blood sugar—it makes it worse. Try broth, crackers, or fruit juice if solid food feels off. And don’t stop insulin, even if you’re not eating. Your body still needs it to process stress hormones. If you’re on insulin, you might need more, not less. Many people panic and cut their dose, which is the wrong move. Talk to your provider ahead of time about your sick day insulin adjustment plan. Keep a written copy on your fridge or phone.

Hydration matters too. Dehydration makes high blood sugar even harder to control. Sip water, sugar-free electrolyte drinks, or broth every 15 to 30 minutes. If you’re vomiting or can’t keep fluids down, call your doctor immediately. Don’t wait for dizziness or confusion. By then, it’s too late.

Some medications make things worse. Over-the-counter cold syrups often have hidden sugar. Decongestants can spike blood sugar. Even some pain relievers can interfere with your kidneys if you’re already dealing with high glucose. Always check labels and ask your pharmacist before taking anything new.

When should you call your doctor? If your blood sugar stays above 300 mg/dL for more than six hours, if ketones are moderate or high, if you’re vomiting for more than two hours, or if you feel confused or have trouble breathing. These aren’t "maybe" signs—they’re red flags. A simple phone call can prevent a trip to the ER.

The diabetes sick day rules aren’t complicated, but they’re easy to forget when you’re feeling awful. That’s why preparation is everything. Write them down. Keep your supplies ready. Practice the steps before you get sick. This isn’t just about numbers—it’s about staying in control when your body is under attack. Below, you’ll find real advice from people who’ve been there, guides on managing insulin during illness, and how to avoid the most common mistakes that send diabetics to the hospital.