When You’re Sick, Your Diabetes Gets Harder
Feeling under the weather is bad enough. But if you have diabetes, a cold, flu, or stomach bug can turn into a medical emergency fast. Your body releases stress hormones like cortisol and adrenaline when you’re sick-even if you’re not eating. These hormones make your liver pump out extra glucose, and they make your body resist insulin. Blood sugar can jump 30% to 50% in just a few hours. That’s why sick day rules aren’t optional. They’re lifesaving.
Never Skip Your Insulin, Even If You Can’t Eat
One of the biggest mistakes people make when they’re sick is skipping their insulin because they’re not eating. That’s dangerous. Your body still needs insulin to keep ketones from building up. Without insulin, your body starts breaking down fat for energy-and that produces ketones. Too many ketones lead to diabetic ketoacidosis (DKA), a life-threatening condition that sends over 27% of diabetes-related hospitalizations in the U.S. every year.
For Type 1 diabetes, you must keep your long-acting insulin (like Lantus, Levemir, or Basaglar) going, even if you’re vomiting or not eating. Most people need to keep at least 80% of their usual basal dose. Some may need to increase it by 10% to 20%, especially if ketones are present. For Type 2 diabetes, you might need to start insulin temporarily during illness, even if you normally take pills. Don’t wait for your doctor to tell you-act early.
If you use an insulin pump, don’t turn it off. Instead, increase your basal rate by 20% for 12 hours if your blood ketones hit 1.0 mmol/L or higher. For those using injections, keep your long-acting insulin and give extra correction doses as needed. Never go more than 4 hours without insulin.
Check Your Blood Sugar Every 2 to 4 Hours
When you’re healthy, checking your blood sugar twice a day might be enough. When you’re sick, you need to check it every 2 to 3 hours if you’re a child, and every 3 to 4 hours if you’re an adult. Write down each number. Look for patterns: Is it rising? Is it staying above 240 mg/dL for more than two checks? That’s your signal to test for ketones.
Here’s what to do based on your numbers:
- If your blood sugar is below 100 mg/dL: Eat 15 grams of fast-acting carbs (like 4 oz of regular soda, 1 tablespoon of honey, or glucose tablets).
- If it’s between 100 and 180 mg/dL: Keep monitoring. You’re in a safe zone, but don’t relax.
- If it’s above 180 mg/dL: Start checking ketones. This is your warning sign.
- If it’s above 240 mg/dL for two checks in a row: Test for ketones immediately.
Don’t wait for symptoms like nausea or confusion. High blood sugar can sneak up fast when you’re sick. Use your meter or CGM. If you have a continuous glucose monitor, watch for trends. If more than half your readings are above 250 mg/dL for 12 hours straight, treat it like a red flag.
Hydration Is Just as Important as Insulin
When your blood sugar is high, your body tries to flush out the extra glucose through urine. That means you lose water-and electrolytes. Dehydration makes everything worse. It raises your blood sugar further and increases your risk of DKA.
Drink fluids constantly. For adults, aim for 6 to 8 ounces every hour. For kids, use the "age in ounces" rule: a 10-year-old should drink 10 ounces per hour. If you’re vomiting, try sipping small amounts every 10 to 15 minutes. Ice chips count too.
What you drink matters. Here’s what to choose based on your blood sugar:
- If your blood sugar is above 180 mg/dL: Stick to sugar-free fluids-water, unsweetened tea, broth, or sugar-free electrolyte drinks.
- If your blood sugar is between 100 and 180 mg/dL: Alternate between water and fluids with 15 grams of carbs per serving. That’s 4 oz of regular soda, 4 oz of Gatorade, or 1/2 cup of apple juice.
- If your blood sugar is below 100 mg/dL: Use sugary fluids to prevent low blood sugar. Avoid diet drinks here.
Keep track. Use a measuring cup. Don’t guess. You need about 8 to 10 cups total per day. If you can’t keep fluids down for more than 4 hours, call your doctor or go to the ER. IV fluids might be needed.
Test for Ketones-And Know What the Numbers Mean
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. That’s when ketones build up-and when DKA starts.
Use a blood ketone meter if you have one. It’s more accurate than urine strips. Urine strips can be misleading-they show ketones from hours ago, not what’s happening now. Blood ketone meters give real-time results.
Here’s what the numbers mean:
- Below 0.6 mmol/L: Normal. No action needed.
- 0.6 to 1.0 mmol/L: Small ketones. Monitor closely. Drink water. Check again in 2 hours.
- 1.0 to 1.5 mmol/L: Moderate ketones. Increase your insulin dose. Drink more fluids. Call your doctor if it doesn’t drop in 4 hours.
- Above 1.5 mmol/L: Large ketones. This is urgent. If you use a pump, change your infusion site immediately. If you’re on injections, give a correction dose and call your doctor or go to the ER. Do not wait.
Never ignore a reading of 1.5 mmol/L or higher. That’s not a "maybe." That’s a red alert. People who wait often end up in the hospital with DKA.
Type 1 vs. Type 2: Key Differences in Sick Day Rules
Not all diabetes is the same. Your sick day plan should match your type.
Type 1 diabetes: You’re at high risk for DKA. Ketone checks are mandatory during any illness. You must never stop insulin. Even if you’re not eating, your body still needs insulin to stop fat breakdown. Your target blood sugar range during illness is 100 to 180 mg/dL. Don’t aim for perfect-aim for safe.
Type 2 diabetes: If you take insulin, treat yourself like a Type 1 person. Check ketones if your blood sugar is over 240 mg/dL. If you’re only on oral meds (like metformin or GLP-1s), you may not need ketone checks unless your blood sugar stays above 240 mg/dL for more than 12 hours. But you still need to monitor closely. Some Type 2 patients need to start insulin temporarily during illness. Don’t assume you’re "safe" just because you don’t use insulin daily.
Also, your blood sugar target during illness is wider: 110 to 180 mg/dL. Tight control isn’t the goal right now. Preventing DKA and dehydration is.
What to Pack in Your Sick Day Kit
Don’t wait until you’re sick to prepare. Build a sick day kit now and keep it in your medicine cabinet or emergency bag.
- Extra insulin (both long-acting and rapid-acting)
- Unexpired ketone test strips (they last 6 months after opening)
- Blood ketone meter (or urine strips as backup)
- Glucose tablets or juice boxes (15g carbs each)
- Sugar-free electrolyte drinks (like Pedialyte Sugar-Free or Gatorade Zero)
- Regular soda or juice (for low blood sugar)
- Measuring cup (to track fluid intake)
- Logbook or app to record blood sugar, ketones, fluids, and insulin doses
- Glucagon emergency kit (if prescribed)
- Over-the-counter meds: Check labels for sugar or alcohol. Avoid cough syrups with high sugar content. Look for "sugar-free" or "diabetic-friendly" versions.
Keep at least a 7-day supply of all your diabetes meds. If you run out during illness, don’t wait. Call your pharmacy or doctor right away.
Red Flags: When to Call 911 or Go to the ER
Some signs mean you need help now. Don’t wait to see if it gets better.
- Cannot keep any fluids down for 4+ hours
- Blood ketones above 1.5 mmol/L
- Blood sugar above 300 mg/dL for two checks with ketones present
- Nausea or vomiting with confusion or drowsiness
- Fast, deep breathing (Kussmaul breathing)
- Fruity-smelling breath
- Unintended weight loss of 5 pounds or more in a few days
If you’re unsure, call your doctor or the ADA helpline at 1-800-DIABETES. They handle 12,000 sick-day calls every month. Better to call and be safe than wait and risk DKA.
Real Stories: What Works-and What Doesn’t
People on Reddit’s r/diabetes community share real experiences. One dad, u/DiabeticDad2020, tried the "age in ounces" rule when his son had the stomach flu. He couldn’t keep fluids down. He ended up in the ER for IV fluids.
Another user, u/Type1Techie, followed the +20% basal rate rule during the flu. His blood sugar stayed between 150 and 200 mg/dL. No DKA. No hospital.
But u/SickDayStruggles got conflicting advice from different doctors. One said to skip insulin when vomiting. The other said never to stop it. He ended up with ketones at 22 mmol/L. He was hospitalized for three days.
These stories aren’t rare. The CDC says 28% of people with low income experience DKA during illness-often because they don’t have access to supplies or clear guidance. Don’t let confusion cost you your health.
What’s Changing in 2025
Guidelines are evolving. In 2023, the ADA updated its sick day rules to include guidance for people using closed-loop insulin systems (like the MiniMed 780G or Omnipod 5). These systems may automatically reduce insulin during illness-but that’s not always safe. Experts now say: don’t rely on automation. Manually override if your blood sugar is high or ketones are present.
The CDC added new advice for viral illnesses like RSV and flu, which cause 37% more insulin resistance than bacterial infections. And by late 2025, the NIH plans to release AI tools that predict sick-day complications based on early symptoms-like cough, fever, or fatigue-before blood sugar spikes.
For now, stick to the basics: keep insulin going, drink fluids, check ketones, and know when to call for help. These rules have saved lives for decades. They still work.
Should I stop taking insulin if I can’t eat when I’m sick?
No. Never stop insulin, even if you’re not eating. Your body still needs insulin to prevent ketone buildup. Skipping insulin during illness is the leading cause of diabetic ketoacidosis (DKA). Keep your long-acting insulin going, and adjust your correction doses based on your blood sugar and ketone levels.
Can I use urine ketone strips instead of blood ketone meters?
Blood ketone meters are more accurate and give real-time results. Urine strips show ketones from hours ago and can be misleading-especially if you’re dehydrated. If you only have urine strips, use them, but treat any moderate or large result as urgent. Upgrade to a blood ketone meter if you can. They’re affordable and widely available.
What if I’m vomiting and can’t keep fluids down?
If you can’t keep any liquids down for more than 4 hours, call your doctor or go to the ER. Dehydration and high blood sugar can spiral fast. You may need IV fluids and insulin in a hospital setting. Don’t wait until you’re dizzy or confused. Early help saves lives.
Are over-the-counter cold medicines safe for diabetics?
Many contain sugar, alcohol, or decongestants that raise blood sugar. Always check labels. Look for "sugar-free," "diabetic-friendly," or "no alcohol" versions. Avoid syrups with high fructose corn syrup. Use pills instead of liquids when possible. If you’re unsure, ask your pharmacist or call your doctor.
How do I know if I’m developing DKA?
Signs of DKA include: blood sugar above 240 mg/dL, ketones above 1.5 mmol/L, nausea or vomiting, fast deep breathing, fruity-smelling breath, confusion, or extreme fatigue. If you have two or more of these, especially with ketones present, seek emergency care immediately. DKA can progress quickly and is life-threatening.
Should I check my weight when I’m sick?
Yes. Unintended weight loss of 5 pounds or more in a few days is a red flag for severe hyperglycemia and possible DKA. Weigh yourself daily during illness. If you’re losing weight despite drinking fluids and taking insulin, call your doctor right away.
Akash Chopda
They say never skip insulin but who really controls the pharma prices? I paid $400 for a vial last month. They want me to check ketones every 2 hours but my meter costs more than my rent. This is a scam wrapped in a guideline.
Sam Jepsen
You got this. Sick days are brutal but you’re not alone. I’ve been through flu season with T1D for 12 years now. Keep that basal going, sip water like it’s your job, and don’t panic when numbers spike. You’re doing better than you think.
Natashia Luu
It is imperative that individuals with diabetes adhere strictly to the protocols outlined herein. Failure to maintain insulin administration during periods of illness constitutes a gross negligence of self-care, and is, in fact, a statistically significant contributor to preventable morbidity. There is no excuse for noncompliance.
akhilesh jha
I read this whole thing and I’m just… confused. Like, I know I’m supposed to keep insulin on, but what if I’m vomiting and my blood sugar is 80? Do I drink juice and risk spiking? Or hold off and risk crashing? Why does no one talk about the middle ground?
Jeff Hicken
i was sick last week and skipped my insuline cuz i was puking and i was fine?? like i didnt die?? maybe the whole ketone thing is hype? also why do they say drink 8 cups?? i drank 2 and lived??
stephanie Hill
I’ve been waiting for someone to say this. The ADA doesn’t care about people who can’t afford test strips. I had to use expired ones last winter. The strips turned pink and then purple and I just… guessed. I cried in the bathroom while my kid slept next to me. This system is designed to fail us.
Jacob McConaghy
As someone who moved from India to the US, I can tell you the difference in care is night and day. Back home, my cousin got sick and had to walk 3 miles to the clinic. Here, you’ve got guidelines, meters, and even sugar-free Pedialyte. It’s not perfect, but we’ve got tools. Use them. Don’t wait until it’s an emergency.
Vineeta Puri
I would like to respectfully emphasize the importance of maintaining consistent insulin administration during periods of physiological stress. Furthermore, adequate hydration remains a cornerstone of metabolic stability. I encourage all individuals to maintain a log of glucose readings, ketone levels, and fluid intake for optimal clinical management.
Victoria Stanley
For anyone reading this and feeling overwhelmed - you’re not alone. I was diagnosed with T1D at 35 and thought I’d never get the hang of sick days. Now I have a kit in my closet with everything labeled. I even color-coded my fluids. It’s not fancy, but it saved me last time I had COVID. You can do this.
Andy Louis-Charles
Blood ketones >1.5? 🚨 Don’t wait. Change your pump site. Drink water. Call your doc. I did this last month - thought I’d be fine. Ended up in the ER at 3am. Don’t be me. 💉💧
Douglas cardoza
I just use the app my endo gave me. It tells me when to bump my basal and what to drink. I don’t even read the article anymore. It just works.
Adam Hainsfurther
I’ve been wondering - how do these guidelines apply to people on GLP-1s? My doctor said I don’t need to check ketones unless I’m over 240 for 12 hours, but I saw someone say that’s risky. Is that true? I don’t want to assume.
Rachael Gallagher
America turns everything into a checklist. You’re sick. You’re poor. You’re brown. You’re old. Now you need 12 tools, 7 apps, and a PhD in endocrinology just to survive a cold. We’re not patients. We’re products.