Metformin During Illness: What You Need to Know Before Stopping or Adjusting Your Dose

When you're sick, your body reacts in ways that can throw your metformin, a common type 2 diabetes medication that helps lower blood sugar by reducing liver glucose production and improving insulin sensitivity. Also known as Glucophage, it's one of the most prescribed drugs for diabetes worldwide. Illness—whether it's a cold, flu, infection, or even severe stress—can cause your blood sugar to rise dramatically. That’s why simply continuing your normal metformin dose isn't always the right move. Many people panic and stop taking it altogether, but that can be just as dangerous. The key is knowing when to hold, when to adjust, and when to call your doctor.

One major risk during illness is lactic acidosis, a rare but serious condition where lactic acid builds up in the bloodstream, often triggered by dehydration, kidney stress, or reduced oxygen flow. Metformin is cleared by your kidneys, and when you're sick—especially with vomiting, diarrhea, or fever—your kidneys can get overwhelmed. If you can't keep fluids down or your kidneys aren't working well, metformin can build up in your system. That’s why doctors often tell patients to pause metformin during severe illness. But here’s the catch: stopping it without replacing it with another plan can cause your blood sugar to soar, leading to diabetic ketoacidosis or hyperosmolar hyperglycemic state. Both are medical emergencies.

It’s not just about the drug—it’s about your whole diabetes management, the ongoing process of monitoring blood sugar, adjusting food, activity, and medication to keep levels stable. During illness, your body releases stress hormones like cortisol and adrenaline. These hormones fight infection but also push your liver to pump out more glucose. Even if you’re not eating, your blood sugar can climb. That’s why checking your blood sugar every 4 hours is critical. If you’re on insulin, you might need extra doses. If you’re only on metformin, you might need to hold it temporarily and rely on hydration and monitoring instead.

Here’s what most people get wrong: they think if they’re not eating, they don’t need their diabetes meds. That’s not true. You still need to manage blood sugar, even if you’re not eating. The goal isn’t to hit your usual target—during illness, it’s to avoid dangerous highs or lows. Keep sipping water. Track your symptoms. Write down your blood sugar readings. Call your provider if your sugar stays above 240 mg/dL for more than a day, if you’re vomiting, or if you feel confused or extremely tired. These aren’t signs you just need more metformin—they’re signs you might need a different approach.

You’ll find real stories in the posts below—people who thought they were doing the right thing by skipping metformin during a stomach bug, only to end up in the ER. Others who kept taking it through a bad flu and ended up with kidney stress. There are guides on how to talk to your pharmacist about sick day plans, how to read your lab results when you’re ill, and what to do if you can’t get your usual meds. This isn’t about guessing. It’s about having a plan before you get sick.