When you’re sick, your body doesn’t just fight off a cold or flu-it fights your diabetes too. Even a minor infection can send blood sugar levels skyrocketing, and if you’re not prepared, that can lead to a life-threatening situation called diabetic ketoacidosis (DKA). The good news? There are clear, proven rules to follow when you’re ill. These aren’t suggestions. They’re survival steps backed by the American Diabetes Association, the International Diabetes Federation, and hospitals like Cleveland Clinic and Mayo Clinic. Skip them, and you risk ending up in the ER. Follow them, and you can get through illness without losing control.
Never Skip Your Insulin-Not Even Once
One of the biggest mistakes people make when they’re sick is stopping their insulin because they’re not eating. That’s dangerous. Your body still needs insulin-even if you’re vomiting or can’t keep food down. When you’re sick, stress hormones like cortisol and adrenaline spike. These hormones make your body resistant to insulin, which means your blood sugar can rise even without food. For Type 1 diabetes, this can trigger ketone production within hours. For Type 2 diabetes on insulin, the same risk exists.
Long-acting insulin (like Lantus, Levemir, or Basaglar) must continue at your regular dose. Never reduce it by more than 20%, and only if your doctor tells you to. If you use an insulin pump, most guidelines recommend increasing your basal rate by 20% for 12 hours when ketones are moderate or large. If you take multiple daily injections, keep your long-acting insulin on schedule. Your short-acting or rapid-acting insulin? You still need it for corrections. Check your blood sugar every 3 to 4 hours (every 2 to 3 hours if you’re a child). If it’s over 240 mg/dL, give a correction dose. Don’t wait. Don’t hope it’ll go down on its own.
Check Ketones-When and How
Ketones are your body’s warning sign that it’s running out of insulin. They’re not a normal part of illness-they’re a red flag. You should test for ketones when your blood sugar hits 240 mg/dL or higher, or if you feel nauseous, have stomach pain, or are breathing fast. Some people wait until they feel awful. Don’t. Test early.
Use a blood ketone meter if you have one. Urine strips are outdated. They’re slow, inaccurate, and can give false negatives. Blood ketone levels tell you what’s happening right now. 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 fluids, retest in 2 hours.
- Above 1.5 mmol/L: High ketones. This is urgent. Call your doctor. If you use a pump, change your infusion site immediately. You may need emergency care.
Studies show that over 70% of DKA cases happen because people didn’t test ketones early enough. If you’ve never used a ketone meter, get one. It’s not optional if you take insulin. The CDC says ketone testing is one of the top three actions that prevent hospitalization during illness.
Stay Hydrated-But Not Just Any Fluid
Dehydration makes everything worse. High blood sugar pulls water out of your cells. Vomiting or fever speeds up fluid loss. Without enough fluids, your kidneys can’t flush out ketones, and your blood sugar climbs even higher.
But not all drinks are equal. Here’s what to drink based on your blood sugar:
- If your blood sugar is under 100 mg/dL: Drink sugary fluids. 4-6 ounces of regular soda, Gatorade, or juice every hour. You’re at risk of low blood sugar now.
- If your blood sugar is between 100-180 mg/dL: Alternate between sugar-free drinks and drinks with 15 grams of carbs. Try 4 oz water + 4 oz Gatorade every hour. This keeps you hydrated without spiking sugar.
- If your blood sugar is over 180 mg/dL: Stick to sugar-free fluids. Water, unsweetened tea, or sugar-free electrolyte drinks. Avoid diet sodas with artificial sweeteners if they upset your stomach.
Adults should aim for 6-8 ounces of fluid every hour. For kids, the rule is simple: drink their age in ounces per hour. A 10-year-old drinks 10 ounces every hour. If you can’t keep fluids down for more than 4 hours, call your doctor. IV fluids might be needed. Don’t wait until you’re dizzy or confused.
What to Eat When You Can’t Eat
You don’t need to eat three meals a day when you’re sick. But you do need carbs-about 15 grams every hour if you can tolerate it. Why? Your body still needs fuel. Without carbs, your liver keeps releasing glucose, and your body breaks down fat for energy, which makes ketones worse.
Easy carb sources:
- 1/2 cup apple sauce
- 1 slice of toast
- 1/2 cup regular pudding
- 1/2 cup of orange juice
- 1 tablespoon of honey or sugar dissolved in water
If you’re vomiting, try small sips every 10-15 minutes. Use a straw. Hold ice chips in your mouth. If you can’t keep anything down for more than 4 hours, get help. This isn’t normal. It’s a sign your body is in distress.
Differences Between Type 1 and Type 2
Not all diabetes is the same when you’re sick. Type 1 diabetes patients are at higher risk for DKA because they have no insulin production. They need ketone checks every time blood sugar is high. Type 2 patients on insulin also need to check ketones. But Type 2 patients on pills only? They usually don’t need ketone testing unless blood sugar stays over 240 mg/dL for more than a day.
However, even Type 2 patients may need insulin during illness. Your body’s stress response can make oral meds ineffective. If your blood sugar stays above 250 mg/dL for more than 24 hours, talk to your doctor. You might need temporary insulin.
Insulin pump users have extra steps. If ketones are high, you must change your infusion set. A clogged or dislodged tube can cause insulin delivery failure. Always carry a backup insulin pen. And if your pump stops working, switch to injections immediately.
What to Keep in Your Sick Day Kit
Don’t wait until you’re sick to prepare. Build a kit now. Here’s what to have on hand:
- Extra insulin (both long-acting and rapid-acting)
- Unexpired blood ketone test strips (check expiration dates-expired strips can give false lows)
- Blood glucose meter with extra batteries
- Glucagon emergency kit (if prescribed)
- 15-gram carb snacks (juice boxes, glucose tablets, honey packets)
- Sugar-free and sugary fluids (electrolyte drinks, juice, water)
- Thermometer, tissues, hand sanitizer
- Written sick day plan from your doctor
Also, keep a log. Write down your blood sugar, ketone levels, fluids taken, and insulin doses. This helps your doctor decide if you need to go to the hospital.
When to Call for Help
You don’t need to tough it out alone. Call your doctor or go to the ER if:
- Your blood sugar stays above 300 mg/dL for two checks in a row
- Your ketones are above 1.5 mmol/L
- You can’t keep fluids down for more than 4 hours
- You’re vomiting for more than 2 hours
- You’re confused, breathing fast, or smell fruity (like nail polish remover)
- You’ve lost 5 pounds or more in a few days
These are not signs to wait out. DKA can develop quickly. In 2022, the CDC found that 27% of diabetes-related hospitalizations were due to DKA during illness. Most of those cases could’ve been prevented with early action.
What About Over-the-Counter Medicines?
Don’t assume OTC meds are safe. Cold and flu medicines often contain sugar, alcohol, or decongestants that raise blood sugar. Check labels. Avoid syrups with high-fructose corn syrup. Choose sugar-free versions. If you’re unsure, ask your pharmacist. One study found that 42% of people didn’t realize their cough syrup spiked their glucose.
Also, avoid alcohol. It can cause dangerous drops in blood sugar, especially if you’re not eating. And never take aspirin if you’re under 18-there’s a rare but serious risk of Reye’s syndrome.
Real Stories, Real Risks
Online communities like Reddit’s r/diabetes are full of lessons learned the hard way. One user, u/SickDayStruggles, told how two different doctors gave conflicting advice-one said to skip insulin when vomiting, the other said never to stop it. He ended up in DKA with ketones at 22 mmol/L. Another, u/Type1Techie, followed the +20% basal rate rule during the flu and kept his blood sugar between 150-200 mg/dL. No ER visit. No hospital stay.
These aren’t just stories. They’re data points. The ADA found that 82% of people who followed sick day rules felt more confident. But 63% said the instructions were confusing, especially for pump users. That’s why clear, consistent guidelines matter.
What’s Changing in 2026?
Guidelines are evolving. The ADA updated its 2023 guidelines to include guidance for continuous glucose monitors (CGMs). If over 50% of your readings are above 250 mg/dL for 12 hours, treat it like a high blood sugar event-check ketones, increase insulin, hydrate. Newer insulin pumps and closed-loop systems are being tested for illness mode, but they’re not ready yet. Don’t rely on automation. You still need to be in charge.
Also, new research shows viral illnesses like RSV and flu cause 37% more insulin resistance than bacterial infections. That means you might need more insulin during cold and flu season than you think.
