Sick Day Rules for Diabetes Medications: Preventing DKA and AKI

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. The biggest dangers? Diabetic ketoacidosis (DKA) and acute kidney injury (AKI). Both can land you in the hospital - and both are often preventable if you know exactly what to do with your diabetes meds when you’re not feeling well.

Here’s the hard truth: 62% of people with diabetes have messed up their medication during illness at least once. Some stopped metformin too late. Others kept taking their SGLT2 inhibitor even after vomiting. A few didn’t realize their blood pressure pill could hurt their kidneys when they weren’t drinking enough. And many just didn’t know when to call for help.

What Happens to Your Body When You’re Sick?

Your body doesn’t know you have diabetes. When you get sick, your stress hormones spike - cortisol, adrenaline, glucagon. These hormones tell your liver to dump more glucose into your blood. That’s fine if you’re healthy. But if you have diabetes, your body can’t handle the extra sugar. Without enough insulin, your body starts breaking down fat for energy. That produces ketones. Too many ketones? That’s DKA.

At the same time, if you’re vomiting, having diarrhea, or just not drinking enough because you feel awful, your blood volume drops. Your kidneys sense that. They start holding onto sodium and water. But if you’re on certain medications - like ACE inhibitors or SGLT2 inhibitors - your kidneys get confused. They can’t filter properly. That’s AKI. It can happen fast. Sometimes in under 24 hours.

Which Medications to Stop - And When

Not all diabetes meds are created equal when you’re sick. Here’s what you need to do based on your prescription.

• Metformin: Stop immediately if you have vomiting, diarrhea, or a fever over 38°C (100.4°F). Why? Metformin can cause lactic acidosis when your kidneys are stressed. A 2019 study of nearly 18,500 people found the risk jumps 8.3 times if your creatinine level rises during illness. You don’t need to wait until you’re dehydrated. The first sign of illness is the signal to pause.
• SGLT2 inhibitors (dapagliflozin, empagliflozin, canagliflozin): Discontinue at the first sign of illness - even if you’re not vomiting yet. The FDA issued a safety alert in 2021 after reviewing over 1,200 cases of euglycemic DKA linked to these drugs. Yes, you read that right: euglycemic. Your blood sugar might look normal (under 14 mmol/L or 250 mg/dL), but your ketones are climbing. This is dangerous because you won’t realize you’re in trouble.
• ACE inhibitors and ARBs (lisinopril, losartan, valsartan): Pause if you’re drinking less than 1,500 mL (about 6 cups) of fluid in 24 hours. These drugs protect your kidneys in normal times, but during dehydration, they can cause your kidney function to crash. A 2022 meta-analysis showed a 40% spike in AKI risk when fluid intake drops below this threshold.
• Insulin: Never stop insulin. Ever. But you may need more. Type 1 patients often need 10-20% more basal insulin every 4 hours if blood sugar stays above 15 mmol/L (270 mg/dL). Type 2 patients on insulin may also need an increase - 68% do, according to a 2023 clinical trial. Don’t guess. Test often. Adjust based on numbers, not how you feel.
• Sulfonylureas (glimepiride, gliclazide): These can cause low blood sugar during illness. If you’re not eating, you may need to reduce the dose. Talk to your provider ahead of time about how much to cut.

How Often to Test - And What to Look For

When you’re sick, checking your blood sugar once a day isn’t enough. You need to check every 2-4 hours. That’s at least 6 times a day. Set alarms on your phone. Write it down. Use the ADA’s free Sick Day Log.

Target range during illness? 100-180 mg/dL (5.6-10 mmol/L). Higher than that? You’re at risk. Lower? You’re at risk of lows. Either way, you need to act.

Now, ketones. If your blood sugar is over 240 mg/dL (13.3 mmol/L), test for ketones. Use urine strips or a blood ketone meter. If blood ketones are above 0.6 mmol/L, call your doctor. If they’re above 1.5 mmol/L, go to the ER. Don’t wait. Don’t try to tough it out. Ketones don’t care how strong you feel.

Watch for signs of AKI too: less urine output, swollen ankles, sudden fatigue, or confusion. If you notice any of these, get help. AKI can develop silently.

Hydration Is Non-Negotiable

You need fluids. Even if you don’t feel like it. Aim for 1.5-2 liters (6-8 cups) of fluid every 24 hours. Water is best. Sugar-free drinks, broth, and electrolyte solutions like Nuun or DripDrop work too.

Dehydration is the silent trigger for both DKA and AKI. If you’re vomiting or have diarrhea, sip small amounts every 15-20 minutes. Don’t gulp. Don’t wait until you’re thirsty. Thirst means you’re already behind.

If you can’t keep fluids down for more than 4 hours, call your provider. If you’ve had diarrhea for over 6 hours, go to urgent care. Time matters.

What to Keep in Your Sick-Day Kit

Don’t wait until you’re sick to prepare. Build a kit now. Keep it in your medicine cabinet or fridge. Include:

• Glucose meter with 50+ test strips
• Ketone strips (urine or blood - get both if you can)
• 7-day supply of all your medications (including insulin)
• 6 bottles of sugar-free drinks (water, tea, soda)
• Electrolyte packets (Nuun, DripDrop, or similar)
• Simple carbs for lows: juice boxes, glucose tablets, honey packets
• ADA Sick Day Log (print it or save it on your phone)

People who prepare this kit ahead of time are 78% less likely to end up in the hospital, according to data from the Joslin Diabetes Center.

When to Go to the Hospital

Call 911 or go to the ER if:

• Your blood sugar stays below 70 mg/dL even after 30g of fast-acting carbs (and you’ve waited 15 minutes)
• Your ketones are over 1.5 mmol/L and haven’t dropped after 2 hours of fluids
• You’ve been vomiting for more than 4 hours
• You’ve had diarrhea for more than 6 hours
• You’re confused, breathing fast and deep (Kussmaul breathing), or smell fruity on your breath
• You haven’t urinated in over 8 hours

These aren’t "maybe" situations. These are red flags. Waiting makes things worse.

Why Guidelines Clash - And What to Do

Here’s the frustrating part: your endocrinologist says one thing. The ADA website says another. Your pharmacist says something else. A Reddit post says to keep taking everything.

The ADA says you can keep metformin during mild illness. The IDF says stop it at the first sign. NICE says to pause meds if you drink less than 1,200 mL. Joslin says "always take your meds unless told otherwise."

So who do you trust?

You trust your provider - but only if they’ve given you written instructions. If they haven’t, here’s the safest approach:

• Stop metformin with any illness involving vomiting or fever
• Stop SGLT2 inhibitors immediately
• Pause ACE inhibitors/ARBs if fluid intake drops below 1,500 mL
• Never stop insulin
• Test glucose and ketones every 2-4 hours
• Hydrate constantly

This is the consensus among experts. Even if your provider’s advice differs, this is the baseline you should follow unless they’ve personally told you otherwise.

What No One Tells You - But Should

Most sick-day guides focus on type 1 diabetes. But 90% of people with diabetes have type 2. And their risks are different.

Older adults with kidney disease, heart failure, or high blood pressure are at the highest risk for AKI. Yet most guidelines don’t adjust for age or comorbidities. A 2023 study found 31% of elderly patients had medication-related complications during illness - even when they followed the rules.

Also, dose matters. Someone on 300 mg of metformin daily has a much lower risk than someone on 2,000 mg. But no guideline accounts for that. You’re treated like a number, not a person.

That’s why you need to know your own numbers: your usual creatinine level, your baseline blood pressure, your typical fluid intake. If your creatinine is normally 0.9 and it jumps to 1.3 during illness, that’s a red flag. If your blood pressure drops below 100/60, that’s a warning. You need to track your own patterns.

What’s Coming Next

There’s hope. AI tools are being tested. Glooko’s Illness Advisor (in beta as of late 2024) uses real-time glucose data to suggest personalized medication changes. The ADA is working on new guidelines for GLP-1 agonists (like semaglutide), which are now used by over 22 million people in the U.S. - but we still don’t have clear sick-day rules for them.

For now, the best tool you have is knowledge. And preparation.

Being sick with diabetes doesn’t have to mean a hospital trip. But you need to act early. Know your meds. Know your numbers. Know your limits. And never ignore the warning signs.