By Warren Howard | December 18, 2025| 10 Comments

Diabetes Medication Safety Checker for Illness

When you're sick with a cold, flu, or stomach bug, your body is under stress. This interactive tool will help you make safe decisions about your diabetes medications. Based on guidelines from the ADA, IDF, and Joslin Center.

Your Medications

Your Symptoms

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Red Flags: If you have any of these symptoms, contact your doctor immediately.

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 minor illness into a medical emergency. Diabetic ketoacidosis (DKA) and acute kidney injury (AKI) don’t wait for you to feel better-they can strike fast, especially if you’re taking the wrong medications at the wrong time. This isn’t about being careful. It’s about knowing exactly what to do with your diabetes meds when you’re too sick to eat, drink, or think clearly.

Why Illness Changes Everything for Diabetes Medications

Your body reacts to infection or fever by releasing stress hormones like cortisol and adrenaline. These hormones make your liver pump out more glucose-even if you’re not eating. At the same time, your body may not use insulin properly. That’s why blood sugar spikes during illness, even in people who usually have good control.

But here’s the real danger: some diabetes medications become risky when you’re dehydrated, vomiting, or not urinating enough. Metformin, SGLT2 inhibitors, and blood pressure drugs like ACE inhibitors or ARBs can turn from helpers into hazards. The risk isn’t theoretical. A 2022 study of nearly 48,000 hospital admissions found that people with diabetes are three times more likely to develop DKA and twice as likely to suffer AKI when sick-and most of these cases were preventable.

Metformin: Stop It When You’re Sick

If you take metformin, you need to know one thing: stop it at the first sign of vomiting, diarrhea, or fever. This isn’t optional. Metformin is cleared by your kidneys. When you’re sick, your kidneys may not work as well. That causes metformin to build up in your blood, increasing your risk of lactic acidosis-a rare but deadly condition where your blood becomes too acidic.

Studies show the risk jumps 8.3 times when your creatinine level rises above 1.5 mg/dL, which happens easily when you’re dehydrated. You don’t need to wait for lab results. If you’re vomiting, have diarrhea, or can’t keep fluids down, pause metformin immediately. Don’t restart it until you’ve been eating and drinking normally for at least 24 hours-and only after checking in with your doctor. Many patients don’t realize this. One Reddit user shared: “I kept taking metformin during my stomach flu. Ended up in the ER with high lactate levels.”

SGLT2 Inhibitors: Immediate Discontinuation Required

Drugs like empagliflozin, dapagliflozin, and canagliflozin help lower blood sugar by making your kidneys flush out glucose. Sounds good-until you’re sick. These medications increase your risk of euglycemic DKA, a dangerous version of ketoacidosis where your blood sugar isn’t sky-high, but your body is still burning fat for fuel and making ketones.

The FDA flagged this in 2021 after reviewing over 1,200 adverse events. The risk jumps 7.2 times when you’re not drinking enough fluids. That’s why you must stop SGLT2 inhibitors the moment you feel ill-even if your blood sugar looks normal. Waiting 24 hours increases your DKA risk by 300%, according to Dr. Anne Peters of USC. Don’t wait for symptoms like fruity breath or nausea. If you’re vomiting, have a fever above 100.4°F (38°C), or feel unusually tired, stop the medication right away.

ACE Inhibitors and ARBs: Watch Your Fluids

If you take lisinopril, ramipril, losartan, or valsartan for blood pressure or kidney protection, you’re at higher risk of AKI when sick. These drugs reduce blood flow to your kidneys. When you’re dehydrated, that reduction becomes dangerous. Your kidneys can shut down quickly.

Research shows a 40% spike in AKI risk when serum creatinine rises more than 0.3 mg/dL in 48 hours-which happens fast during vomiting or diarrhea. The rule? Pause these medications if you’re drinking less than 1,500 mL (about 6 cups) of fluid in 24 hours. That’s not much. If you’re sipping water but not keeping it down, stop the pill. Recheck with your doctor before restarting. Don’t assume your blood pressure is the only thing at risk. Your kidneys are too.

Person at ER entrance holding red-alert ketone strip, other meds falling away.

Insulin: Never Skip It

Insulin is the one medication you almost never stop-even when you can’t eat. Skipping insulin during illness is one of the biggest mistakes people make. Without insulin, your body breaks down fat for energy, creating ketones. That’s how DKA starts.

For type 1 diabetes: Increase your basal insulin by 10-20% every 4 hours if your blood sugar is above 15 mmol/L (270 mg/dL). Test every 2-4 hours. If ketones are above 0.6 mmol/L, call your doctor. For type 2 diabetes: Most people need more insulin when sick. A 2023 trial found 68% of type 2 patients on insulin needed higher doses during illness. Don’t guess. Use your sick-day plan. If you don’t have one, ask your provider for it now.

What to Do: The Sick Day Checklist

Don’t wait until you’re sick to figure this out. Prepare now. Here’s what to have ready:

  • Glucose meter with 50+ test strips
  • Ketone test strips (urine or blood)
  • 7-day supply of all your medications (in case you can’t get to the pharmacy)
  • 6 bottles of sugar-free fluids (water, broth, sugar-free electrolyte drinks)
  • 15g fast-acting carbs (juice, glucose tablets) for lows
  • ADA Sick Day Log (print or save on your phone)

When you get sick:

  1. Test blood sugar every 2-4 hours (minimum 6 times a day)
  2. Check ketones if blood sugar is above 240 mg/dL (13.3 mmol/L)
  3. Stop metformin if vomiting or diarrhea starts
  4. Stop SGLT2 inhibitors if fever >100.4°F (38°C)
  5. Pause ACE inhibitors/ARBs if you’re drinking less than 1,500 mL/day
  6. Keep taking insulin-even if you’re not eating
  7. Drink fluids: 2-3 liters per day if possible
  8. Call your doctor if ketones stay high for more than 2 hours, or if you’ve been vomiting for over 4 hours

Red Flags: When to Go to the ER

You don’t need to wait until you’re unconscious. These signs mean get help now:

  • Blood sugar below 70 mg/dL and doesn’t rise after 15g carbs
  • Blood ketones above 1.5 mmol/L or urine ketones >1.5 mmol/L
  • Vomiting for more than 4 hours
  • Diarrhea for more than 6 hours
  • Difficulty breathing or fruity-smelling breath
  • Confusion, drowsiness, or extreme fatigue
  • Little or no urine output

These aren’t “maybe” situations. They’re emergencies. DKA and AKI can kill within hours if untreated.

Sick-day kit with test strips, water, and insulin neatly arranged on a shelf.

Why Guidelines Conflict-and What to Do

Not all advice is the same. The ADA says you can keep metformin during mild illness. The IDF says stop it at the first sign of sickness. NICE says pause meds if you drink under 1,200 mL. Joslin Center says “always take your meds unless your doctor says otherwise.”

That’s confusing-and dangerous. A 2024 survey found 62% of patients had at least one medication mistake during illness. One patient told me: “My endocrinologist said keep metformin. My GP said stop it. I didn’t know who to trust.”

Here’s the fix: go with the most conservative, safest rule. If there’s doubt, stop the medication. It’s safer to pause metformin or SGLT2 inhibitors for a few days than risk lactic acidosis or DKA. Always confirm with your provider when you’re well again.

What You Can Do Today

Don’t wait until you’re sick to learn this. Right now, do three things:

  1. Make a sick-day kit with the items listed above. Keep it in your medicine cabinet.
  2. Write down your sick-day plan: which meds to stop, when, and who to call.
  3. Share it with a family member or friend. Give them a copy.

Most people who avoid hospitalization during illness had a plan. They didn’t guess. They didn’t wait. They acted.

Frequently Asked Questions

Should I stop my diabetes meds if I have a fever?

Yes-if you take SGLT2 inhibitors (like empagliflozin or dapagliflozin), stop them immediately. For metformin, stop if you have fever along with vomiting or diarrhea. For insulin, never stop. For ACE inhibitors or ARBs, pause if you’re not drinking enough fluids. Fever means your body is under stress, and that changes how your medications work.

Can I take over-the-counter cold medicine with diabetes?

Yes, but be careful. Avoid sugary syrups and decongestants like pseudoephedrine, which can raise blood sugar. Choose sugar-free versions. Check labels for hidden sugars or alcohol. If you’re unsure, ask your pharmacist. Some cold meds can also affect kidney function-especially if you’re already on ACE inhibitors or ARBs.

What if I can’t eat during illness?

You still need calories. Try clear broths, gelatin, popsicles, or sugar-free electrolyte drinks. If you can’t keep food down, drink fluids with 15g of carbs every hour (like regular ginger ale or juice) to prevent low blood sugar. Never skip insulin. You might need less, but you still need some. Test your blood sugar often and call your doctor if you’re not able to take in any carbs for more than 4 hours.

How often should I test my blood sugar when sick?

At least every 2 to 4 hours-so at least 6 times a day. If your blood sugar is rising quickly or you have ketones, test every hour. Don’t rely on how you feel. You can feel fine and still be heading for DKA. Use a log to track readings, ketones, fluids, and medications. This helps your doctor give you better advice later.

Is it safe to use ketone strips at home?

Yes, and it’s essential. Urine ketone strips are affordable and easy to use. Blood ketone meters are more accurate but cost more. Test when your blood sugar is above 240 mg/dL or if you feel nauseous, tired, or have stomach pain. Ketones above 1.5 mmol/L mean you need medical help. Don’t wait for symptoms to get worse.

When can I restart my medications after being sick?

Don’t restart on your own. Wait until you’re eating and drinking normally for at least 24 hours. Then call your doctor. They’ll check your kidney function (creatinine) and blood sugar control before telling you when to restart metformin, SGLT2 inhibitors, or blood pressure meds. Restarting too soon is a leading cause of preventable AKI.

Next Steps

If you have diabetes and haven’t created a sick-day plan, do it today. Talk to your doctor about your specific medications. Write down what to stop, what to keep, and who to call. Print it. Save it on your phone. Give a copy to someone you trust.

For those managing diabetes long-term, this isn’t just advice-it’s a survival skill. You’ve learned to count carbs, check blood sugar, and adjust insulin. Now you’ve learned how to protect your kidneys and avoid DKA when your body is under attack. That’s not just smart. It’s life-saving.