Metformin Diarrhea: What Happens and How to Deal With It

If you’ve started metformin for type 2 diabetes, a sudden run‑to‑the‑bathroom can feel like an unwelcome surprise. You’re not alone – up to one in three people on the drug report loose stools at some point. The good news is that most cases are mild and easy to manage without stopping your medication.

Why Metformin Can Upset Your Stomach

Metformin works by lowering glucose production in the liver and helping your cells absorb sugar more efficiently. Part of that action happens right in the gut: the drug increases the amount of glucose that stays in the intestines, which draws water into the bowels and speeds up movement. It also changes the balance of good bacteria, leading to fermentation that can cause gas and loose stools.

People who take a high dose all at once, skip meals, or have a sensitive gut are most likely to notice diarrhea. The extended‑release (XR) version delivers the drug more slowly, which often reduces this side effect.

Practical Ways to Reduce Diarrhea

Split your dose. Instead of one big tablet in the morning, try two smaller doses with breakfast and dinner. This spreads out the glucose‑drawing effect and gives your gut time to adjust.

Take it with food. A solid meal slows down how fast metformin reaches the intestines. Even a light snack can make a big difference compared to taking the pill on an empty stomach.

Stay hydrated. Diarrhea can deplete fluids and electrolytes quickly. Sip water throughout the day, and consider adding a pinch of salt or an electrolyte drink if you’re losing a lot.

Try probiotics. A daily probiotic with strains like Lactobacillus or Bifidobacterium may help rebalance gut bacteria and cut down on loose stools. Look for a product that guarantees live cultures through the expiration date.

Talk to your doctor about XR metformin. The extended‑release formula often cuts diarrhea in half while keeping blood‑sugar control strong. Your prescriber can switch you safely if needed.

If diarrhea lasts more than a week, is very watery, or comes with severe abdominal pain, fever, or weight loss, call your healthcare provider. Those signs could mean an infection or another condition that needs attention.

Most people find that a few small tweaks—splitting the dose, eating before the pill, drinking more water—make metformin tolerable again. By staying proactive and communicating with your doctor, you can keep the medication working for you without constant bathroom trips.