Metformin: What It Does, How to Take It, and Safety Tips
Metformin is the most prescribed oral drug for type 2 diabetes. It lowers blood sugar mainly by reducing glucose production in the liver and improving insulin sensitivity. Many people also use it for PCOS to help with insulin resistance. If your doctor suggested metformin, this page gives the basics you need to take it safely and get the best results.
Start low and go slow. Typical starting doses are 500 mg once or twice daily with food. Doctors often increase the dose every one to two weeks to balance benefit and side effects. A common effective dose is 1500–2000 mg per day split into two or three doses. If you take an extended-release (XR) form, once-daily dosing at night is common.
How to take metformin and reduce side effects
Take metformin with a meal to cut down stomach upset. Nausea, diarrhea, and abdominal discomfort are the most common side effects. If these start, don’t stop immediately—talk to your prescriber about lowering the dose or switching to XR. Staying hydrated and spreading the dose across meals can help. If diarrhea is severe or persistent, contact your healthcare team.
Watch for B12 drop. Metformin can lower vitamin B12 over time, which may cause fatigue or numbness. Ask your doctor to check B12 every year or if you notice symptoms. A simple blood test tells you if you need supplements.
Safety checks, interactions, and when to pause metformin
Your kidney function matters. Metformin is cleared by the kidneys, so doctors check eGFR before starting and annually after that. If your eGFR falls below a certain level, your provider may lower the dose or stop metformin. Also pause metformin around major contrast scans, surgery, or any episode that can cause dehydration or severe infection—these situations raise the small risk of lactic acidosis.
Limit heavy drinking. Excess alcohol increases the risk of low blood sugar and can raise lactic acidosis risk while on metformin. Tell your provider about any other drugs you take—some medicines and supplements can interact or affect kidney function.
Expect results in weeks. You’ll usually see a drop in fasting glucose and A1c within weeks to months. Your clinician will track A1c, kidney tests, and sometimes weight. Metformin can help with modest weight loss or weight stability for many people.
If metformin doesn’t control your blood sugar, there are other options. We have a detailed guide on effective alternatives that explains different drug classes and pros and cons. Always discuss changes with your provider—they’ll match choices to your health, goals, and risks.
Bottom line: metformin is effective, affordable, and generally safe when used with proper checks. Take it with food, monitor kidney function and B12, avoid heavy alcohol, and keep open communication with your healthcare team.
May, 1 2025