When you’re sick, your body fights infection by releasing stress hormones like cortisol and adrenaline. For someone with diabetes, this isn’t just a cold or flu-it’s a metabolic emergency waiting to happen. Blood sugar can spike even if you’re not eating. Insulin resistance surges. Ketones build up. And if you don’t act fast, you could end up in the hospital with diabetic ketoacidosis (DKA). That’s why sick day rules for diabetes aren’t optional. They’re life-saving.

Why Illness Changes Everything for People with Diabetes

When you have a cold, flu, or even a stomach bug, your body goes into survival mode. It doesn’t care about your meal plan or your insulin schedule. It’s pumping out hormones that tell your liver to dump glucose into your bloodstream. That’s fine for someone without diabetes. But if you have Type 1 or insulin-requiring Type 2 diabetes, your body can’t handle that extra sugar. Without enough insulin, your body starts breaking down fat for energy-and that creates ketones. Too many ketones? That’s DKA. It’s dangerous. It can kill.

According to the CDC, about 27% of all diabetes-related hospitalizations are due to DKA triggered by illness. And in severe cases, the death rate is between 2% and 5%. The worst part? Most of these cases happen because people stop their insulin when they’re sick. They think, “I’m not eating, so I don’t need insulin.” That’s wrong. Always wrong.

Never Skip Your Long-Acting Insulin

This is the single most important rule. Never stop your long-acting insulin-not even for a day. Whether you take Lantus, Levemir, Basaglar, or another basal insulin, it’s still working in your body even when you’re not eating. It’s keeping your liver from dumping too much glucose and preventing ketone production. If you skip it, you’re essentially turning off your body’s only safety net.

People with Type 1 diabetes must keep at least 80% of their usual basal dose, even during vomiting or fasting. For Type 2 patients on insulin, the same rule applies. You might need more, not less. Studies show insulin resistance can increase by 30-50% during illness. That means your usual dose might not be enough. Don’t guess. Test. Adjust. Call your provider if you’re unsure.

Check Your Blood Sugar Every 2-4 Hours

You can’t manage what you don’t measure. During illness, check your blood sugar at least every 3-4 hours if you’re an adult. If you’re a child or teenager, check every 2-3 hours. Some guidelines say to start checking as soon as you feel unwell-even before your sugar rises.

Here’s what to do based on your numbers:

• Below 100 mg/dL: You’re at risk for low blood sugar. Take 15 grams of fast-acting carbs (like juice or glucose tablets). Recheck in 15 minutes.
• 100-180 mg/dL: This is your target range during illness. Keep hydrating. Keep insulin going.
• 180-240 mg/dL: You need extra insulin. Use your correction dose as usual. Don’t hold back.
• Over 240 mg/dL: Test for ketones immediately. If you’re using a CGM, look for a steady upward trend over several hours.

Many people wait until their sugar hits 300 mg/dL to act. That’s too late. By then, ketones may already be building. Start checking at 240 mg/dL. That’s the red flag.

Ketone Checks: When, How, and What to Do

Ketone testing isn’t optional when you’re sick and your blood sugar is high. You need to know if your body is burning fat for fuel. There are two ways to test: blood ketone meters and urine strips. Blood ketone meters are more accurate and faster. Urine strips can be misleading-they show ketones from hours ago, not right now.

Test for ketones when:

• Your blood sugar is over 240 mg/dL
• You have nausea, vomiting, or stomach pain
• You’re feeling unusually tired or confused

Here’s what the numbers mean:

• Below 0.6 mmol/L: Normal. Keep monitoring.
• 0.6-1.5 mmol/L: Moderate ketones. Increase insulin. Drink more fluids. Recheck in 2 hours.
• Over 1.5 mmol/L: High ketones. Call your doctor immediately. If you use an insulin pump, change your infusion site. This is a medical alert.

Urine ketone results? “Small” or “trace” means monitor closely. “Moderate” or “large” means treat like blood ketones over 1.5 mmol/L. Don’t wait. Don’t ignore it.

Hydration: The Silent Lifesaver

When your blood sugar is high, your body tries to flush out the extra glucose through urine. That means you’re losing water fast. Dehydration makes everything worse-it thickens your blood, makes insulin less effective, and speeds up ketone buildup.

Drink fluids constantly. Not just water. You need the right balance of sugar and electrolytes.

Here’s the hydration plan:

• If your blood sugar is below 100 mg/dL: Drink fluids with sugar. 4-8 oz of regular soda, juice, or sports drink every hour.
• If your blood sugar is 100-180 mg/dL: Alternate between sugar-free fluids (water, diet soda) and fluids with 15g carbs (like half juice/half water). Aim for 6-8 oz every hour.
• If your blood sugar is over 180 mg/dL: Stick to sugar-free fluids. Water, unsweetened tea, broth, or sugar-free electrolyte drinks.

For kids, some guidelines suggest drinking “age in ounces” per hour (a 10-year-old drinks 10 oz/hour). That’s a good starting point, but adjust based on vomiting or diarrhea. If you can’t keep fluids down for more than 4 hours, go to the ER. IV fluids can save your life.

Special Considerations: Pump Users, Type 2, and Kids

If you use an insulin pump, your sick day rules are a bit different. You can’t just skip your basal rate. If ketones are moderate or high, increase your basal rate by 20% for 12 hours. Keep giving correction doses. Change your infusion set if your ketones stay high-it might be a blocked tube, not your body needing more insulin.

People with Type 2 diabetes who don’t usually take insulin may need to start it during illness. Your doctor might give you a short-term insulin plan. Don’t refuse it. Your body is under stress. Oral meds won’t cut it.

For children, dehydration and DKA happen faster. Watch for dry lips, no tears, less urination, or lethargy. Check blood sugar and ketones more often. Keep a sick-day kit ready: glucose tabs, ketone strips, insulin, fluids, and a list of emergency contacts.

What to Keep in Your Sick-Day Kit

Don’t wait until you’re sick to prepare. Build a kit now. Here’s what you need:

• Extra insulin (both rapid-acting and long-acting)
• Unopened ketone test strips (they expire 6 months after opening)
• Blood ketone meter with extra batteries
• Glucose tablets or juice boxes
• Sugar-free electrolyte drinks
• Measuring cup (for accurate fluid intake)
• Thermometer, pain relievers (acetaminophen only-avoid NSAIDs like ibuprofen if you have kidney issues)
• List of emergency contacts and your doctor’s number

Check your kit every 3 months. Replace expired strips. Make sure your insulin hasn’t been exposed to heat.

What Not to Do

There are a lot of myths out there. Don’t fall for them:

• Don’t skip insulin-even if you’re not eating.
• Don’t rely on urine strips if you have a blood ketone meter.
• Don’t drink alcohol-based cough syrups-they spike sugar.
• Don’t wait for vomiting to start before taking action.
• Don’t assume you’re fine just because you feel “not that sick.”

One Reddit user, u/SickDayStruggles, shared: “Different doctors told me to skip insulin when vomiting versus never skip it. I ended up in DKA with ketones at 22 mmol/L.” That’s not a scare story. That’s a real person who almost died because of conflicting advice. Don’t let that be you.

When to Call Your Doctor or Go to the ER

You don’t have to figure this out alone. Call your doctor if:

• Your ketones are over 1.5 mmol/L and not coming down after 2 correction doses
• You’ve been vomiting for more than 4 hours
• Your blood sugar stays over 300 mg/dL for more than 6 hours
• You’re confused, having trouble breathing, or smell fruity on your breath
• You’ve lost 5 pounds or more in a few days

These are emergency signs. Don’t wait. Go to the ER. DKA is treatable-but only if caught early.

Final Thoughts: Be Ready Before You Get Sick

Sick day rules for diabetes aren’t complicated. But they require discipline. You have to check your numbers more often. You have to drink when you don’t feel like it. You have to give insulin when you think you shouldn’t. It’s hard. But it’s worth it.

Every year, thousands of people with diabetes end up in the hospital because they didn’t follow these rules. You don’t have to be one of them. Prepare your kit. Know your numbers. Trust your meter. And never, ever stop your insulin.