Managing Blood Sugar on Sick Days with Type 1 Diabetes: What You Need to Know

There's nothing quite like coming down with a cold or stomach bug when you have Type 1 Diabetes. What would be a miserable-but-manageable few days for most people can turn into a full-on blood sugar rollercoaster for us. Glucose spikes out of nowhere, ketones creep up, and your usual routines go completely out the window.

If you've ever wondered why getting sick makes your blood sugar so much harder to control — or what you can actually do about it — this one's for you. Let's break down the basics of sick day management for T1D in a way that's practical and easy to follow, even when you're running on tissues and tea.

Why Does Being Sick Mess with Blood Sugar?

When your body is fighting an infection or illness, it releases stress hormones like cortisol and adrenaline. These hormones are part of your immune response — they help your body mobilize energy to fight off whatever is attacking it. The problem is, those same hormones trigger your liver to release glucose and make your cells more resistant to insulin.

The result? Blood sugars that climb even when you're barely eating. It can feel completely illogical — you're lying in bed, skipping meals, and your CGM is still showing arrows pointing up. This is completely normal in T1D, and it's one of the reasons sick days deserve their own management strategy.

What About Stomach Bugs?

Gastroenteritis (vomiting and diarrhea) adds another layer of complexity. If you can't keep food or fluids down, your blood sugar might actually drop. But dehydration can concentrate your blood glucose and send it higher. And if your body starts breaking down fat for fuel because it's not getting enough glucose, ketones can develop — even without extremely high blood sugar.

This is why sick days with T1D require closer monitoring, not less.

Sick Day Essentials: What to Have on Hand

Being prepared before you get sick makes everything easier. Try to keep a "sick day kit" somewhere accessible:

• Ketone testing strips or a blood ketone meter — urine strips work, but blood ketone meters give faster, more accurate readings

• Electrolyte drinks (look for low-sugar or sugar-free versions, or plain ones you can sip slowly)

• Easy-to-digest carbs — crackers, plain rice, toast, or glucose tablets for lows

• A thermometer

• Your diabetes care team's sick day contact number — know when to call

• Extra insulin supplies — including syringes or pens as a backup if you use a pump

Having these things ready means you're not scrambling when you feel terrible.

Practical Tips for Managing T1D on Sick Days

1. Check Your Blood Sugar More Often

This isn't the time to rely on a single glance at your CGM every few hours. Aim to check (or review your CGM readings) every one to two hours. Sick day blood sugars can move fast, and catching a trend early gives you more time to respond calmly.

2. Test for Ketones

If your blood sugar is running high — many care teams suggest checking ketones when you're consistently above 14 mmol/L (250 mg/dL) — test for ketones. Moderate to large ketones alongside high blood sugar can be a sign of diabetic ketoacidosis (DKA), which is a medical emergency. Don't wait to see if it resolves on its own. Contact your diabetes team or seek emergency care if ketones are high.

3. Keep Drinking Fluids

Dehydration makes everything worse and can push blood sugar higher. Sip water, sugar-free electrolyte drinks, or broth regularly throughout the day. Even small sips every 15 minutes add up. If you're vomiting and genuinely can't keep anything down, that's a signal to call your care team or go to urgent care.

4. Don't Stop Your Basal Insulin

This is one of the most important sick day rules for T1D: never stop your background (basal) insulin, even if you're not eating. Your body still needs it. Stopping basal insulin dramatically increases your risk of DKA. If you're on a pump, keep it running unless your care team advises otherwise.

5. Eat What You Can, When You Can

If you can eat, try to stick to easy-to-digest, lower-fat foods that won't cause huge glucose swings. Plain crackers, toast, rice, or broth-based soups are good options. If you're struggling to eat at all, even small amounts of carbohydrate can help keep your glucose stable and prevent ketones.

6. Adjust Your Meal Tracking — But Keep Tracking

Using an app like iSpike to log what you're eating is still valuable on sick days, even if your meals are minimal or irregular. Tracking helps you (and your care team) understand what was happening during the illness if you need to review patterns afterward. It also keeps you in the habit of logging, which is easier to maintain than restart.

7. Know When to Call for Help

Contact your diabetes care team or go to the emergency department if:

• Ketones are moderate or high

• You've been vomiting for more than a few hours and can't keep fluids down

• Your blood sugar won't come down despite correction

• You feel confused, are breathing rapidly, or feel very unwell

DKA can develop quickly in T1D, and it's always better to make the call and be told you're fine than to wait too long.

After You Recover: Getting Back to Baseline

Once you're feeling better, your blood sugars may still be unpredictable for a day or two as your body recovers. Be patient with yourself. Resume your normal eating and insulin routine gradually, and keep an eye on your CGM data for any lingering patterns. Your care team can help you review what happened and adjust your plan if needed.

Sick days are genuinely hard with T1D — there's no sugarcoating it. But with a bit of preparation and a clear plan, you can get through them safely and come out the other side feeling more confident about handling whatever comes next.

This article is for informational purposes only and does not replace advice from your diabetes care team.