When you’re sick with a cold, flu, or stomach bug, your body is under stress. For people with diabetes, that stress can turn a simple illness into a medical emergency. Diabetic ketoacidosis (DKA) and acute kidney injury (AKI) aren’t rare complications-they happen 300% more often during illness, according to a 2022 JAMA study of nearly 48,000 hospital admissions. And the biggest culprit? Not eating right, not drinking enough, or worse-taking the wrong diabetes meds at the wrong time.
Why Sick Days Are Dangerous for People with Diabetes
Your body doesn’t know the difference between a fever from the flu and a spike in blood sugar. When you’re sick, your liver dumps extra glucose into your bloodstream. At the same time, your body can’t use insulin properly. That’s why your blood sugar can skyrocket-even if you’re not eating. And if you’re vomiting, diarrhea, or just too tired to drink, your kidneys struggle. That’s when medications like metformin or SGLT2 inhibitors become risks, not helpers.
Here’s the hard truth: 12.7% of all diabetes-related hospitalizations happen because someone kept taking their meds the same way they do when they’re healthy. That’s over 150,000 people in the U.S. every year. Most of those cases are preventable.
Medication-Specific Rules: What to Stop and When
Not all diabetes meds are created equal when you’re sick. Some need to be paused immediately. Others need to be adjusted. And some? You keep taking them.
Metformin-Stop it the moment you start vomiting, have diarrhea, or develop a fever. Why? Because metformin builds up in your blood when your kidneys aren’t flushing fluids properly. That raises your risk of lactic acidosis-a rare but deadly condition. A 2019 NEJM study showed an 8.3-fold increase in risk when creatinine levels rise above 1.5 mg/dL. Don’t wait for a lab test. If you’re dehydrated, stop metformin.
SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin)-These drugs are dangerous during illness. They make your body flush sugar through urine, even when your blood sugar isn’t high. That’s called euglycemic DKA, and it’s sneaky. You can feel awful, have fruity breath, and be in ketoacidosis-even with blood sugar at 180 mg/dL. The FDA issued a safety alert in 2021 after 1,247 reports of DKA linked to these drugs during illness. Stop them at the first sign of vomiting, fever, or reduced fluid intake. Don’t wait 24 hours. Waiting increases your DKA risk by 300%, says Dr. Anne Peters, a leading diabetes expert.
ACE inhibitors and ARBs (lisinopril, losartan, valsartan)-These blood pressure meds are fine when you’re well. But when you’re sick and not drinking enough, they can cause your kidneys to shut down. A 2022 meta-analysis found a 40% higher risk of AKI when fluid intake drops below 1,500 mL per day. If you’re sipping water but not eating or drinking normally, pause these meds. Call your doctor before restarting them.
Insulin-This is the one you almost always keep taking. In fact, you may need more. Type 1 patients should increase basal insulin by 10-20% every 4 hours if blood sugar stays above 15 mmol/L (270 mg/dL). Type 2 patients on insulin? About 68% need higher doses during illness, according to a 2023 Diabetes Care trial. Don’t skip your long-acting insulin. Even if you’re not eating, your liver is still pumping out sugar. Skipping insulin = higher ketones = higher risk of DKA.
What to Do: The 5-Day Rule and Monitoring
There’s a simple rule doctors agree on: Don’t restart any stopped medication after 5 days without talking to your provider. Dr. Robert Gabbay from the ADA says restarting meds too soon causes 18% of preventable AKI cases. You might feel better, but your kidneys may still be stressed.
Monitor your blood sugar every 2-4 hours. That’s at least 6 checks a day. Use a glucose meter with test strips you’ve kept on hand. Target range during illness? 100-180 mg/dL. Don’t panic if it’s a little high-focus on trends. If your sugar is climbing fast, that’s your signal to act.
Test for ketones if your blood sugar is over 240 mg/dL. Use urine strips or a blood ketone meter. If your blood ketones are above 0.6 mmol/L, or urine ketones are over 1.5 mmol/L, call your doctor or go to the ER. Don’t wait. Ketones mean your body is burning fat for fuel because it can’t use glucose. That’s the start of DKA.
Hydration Is Non-Negotiable
You can’t out-drug dehydration. If you’re vomiting or have diarrhea, you’re losing fluids-and electrolytes. Drink water, sugar-free broth, or electrolyte drinks like Nuun or Pedialyte. Avoid sugary sodas unless you’re treating low blood sugar.
Track your fluid intake. Aim for at least 1,500 mL (about 6-7 cups) per day. If you can’t keep that down, you’re at risk. That’s when you need to call your doctor, not just “wait it out.”
What to Pack in Your Sick-Day Kit
Don’t wait until you’re sick to prepare. Build your kit now. Here’s what to keep on hand:
- Glucose meter with 50+ test strips
- Ketone test strips (urine or blood)
- 7-day supply of all your diabetes meds (including insulin)
- Sugar-free beverages (water, diet soda, broth)
- Electrolyte packets (Nuun, Pedialyte)
- Fast-acting carbs (glucose tabs, juice boxes, honey packets)
- ADA Sick Day Log (print or digital)
People who use a sick-day kit are 78% less likely to end up in the hospital, according to Joslin Diabetes Center data. This isn’t optional. It’s your safety net.
When to Call for Help
You don’t need to guess when it’s time to go to the ER. Here are the red flags:
- Blood sugar below 70 mg/dL and doesn’t improve after 30g of carbs
- Ketones above 1.5 mmol/L for more than 2 hours
- Vomiting for more than 4 hours
- Diarrhea for more than 6 hours
- Confusion, trouble breathing, or fruity-smelling breath
- Little or no urine output, swollen ankles, or extreme fatigue
If you have any of these, call your doctor or go to urgent care. Don’t wait until you’re collapsed. DKA and AKI can progress fast.
Confusing Advice? You’re Not Alone
Many patients report conflicting advice. One endocrinologist says stop metformin. Another says keep it. The ADA says one thing. The IDF says another. NICE recommends lower fluid thresholds. And Joslin Diabetes Center says, “Just take your meds unless told otherwise.”
A 2024 survey found 41% of patients got contradictory instructions from their primary care doctor and their endocrinologist. That’s dangerous. Here’s what to do: Write down your doctor’s specific instructions during your next visit. Ask: “What meds do I stop if I’m vomiting? What if I can’t drink? When do I call?” Get it in writing. Keep it in your sick-day kit.
What’s Missing in Current Guidelines
Experts agree: current rules are too one-size-fits-all. A person taking 300mg of metformin daily has a much lower risk than someone on 2,000mg. But the guidelines don’t reflect that. Elderly patients with heart or kidney disease are at higher risk, but the rules don’t account for comorbidities. And GLP-1 agonists (like Ozempic or Mounjaro)-used by 22 million Americans-have no clear sick-day protocols yet.
AI tools like Glooko’s Illness Advisor (in beta as of late 2024) are starting to change that. They use your real-time glucose data to suggest personalized adjustments. But until those are standard, you need to be your own advocate.
Final Takeaway: Be Prepared, Not Scared
Sick days don’t have to mean hospital stays. The data is clear: following the right rules cuts DKA risk by 73% in type 1 patients. The tools exist. The knowledge is out there. What’s missing is consistency and preparation.
Don’t wait until you’re sick to figure this out. Build your kit. Know your meds. Write down your plan. Practice calling your doctor. And remember-when you’re ill, your body is fighting two battles: the virus and your blood sugar. You can’t win one without managing the other.
Stay hydrated. Test often. Stop the wrong meds. Keep the right ones. And never be afraid to call for help.
