Metformin: What It Does and How to Use It Safely

Metformin is the most common pill for type 2 diabetes. It lowers blood sugar mainly by cutting how much sugar your liver makes and by helping your body use insulin better. If you or someone you care for was just prescribed metformin, this page gives straight, useful facts so you know what to expect and when to call your doctor.

Who should take metformin and why

Doctors prescribe metformin first for most people with type 2 diabetes because it works well and usually has fewer risks than many other options. It can help with weight control for some people and may lower the long-term risk of heart problems. Your doctor might suggest metformin alone or with other drugs, depending on your blood sugar levels and other health issues.

Metformin also shows up in prediabetes care and sometimes for conditions like polycystic ovary syndrome (PCOS). But it isn’t right for everyone — people with severe kidney problems, certain heart or liver diseases, or those prone to heavy alcohol use may need a different plan.

Common side effects and how to manage them

The most common side effects are stomach-related: nausea, diarrhea, gas, and a bit of belly discomfort. These usually ease after a few weeks. To reduce them, start with a low dose and take metformin with food. Extended-release (XR) versions can also be gentler on the stomach.

Serious but rare issues include lactic acidosis, a buildup of acid in the blood. It’s uncommon but serious — signs include unusual tiredness, trouble breathing, muscle pain, dizziness, or stomach pain with chills. If you get any of those, seek care right away.

Metformin can affect vitamin B12 levels over time. Your doctor may check B12 at least once a year, especially if you have numbness or tingling in hands or feet, or unexplained fatigue.

Dosing often starts at 500 mg once or twice daily, then the doctor increases it gradually. Maximum daily doses vary by product, often up to 2000–2500 mg depending on the formulation. Don’t change dose without medical advice.

Important checks: doctors monitor kidney function before starting metformin and during treatment because the kidneys clear the drug. If kidney numbers fall, your doctor may lower the dose or stop metformin temporarily, especially around surgeries, contrast scans, or serious illnesses.

Practical tips: take metformin with a meal to cut stomach upset, store it at room temperature, and keep a list of all your meds to avoid interactions. Tell any provider you’re taking metformin before imaging tests or anesthesia.

If you have questions about side effects, dose changes, or how metformin fits into your overall plan, ask your doctor or pharmacist. They can tailor advice to your health, other meds, and lab results so you get the most benefit with the least risk.