Metformin: What it Does, How to Take It, and Smart Safety Tips

Metformin is the go-to pill for type 2 diabetes because it lowers blood sugar without usually causing weight gain. It works mainly by cutting liver glucose production and helping your body use insulin better. Doctors also prescribe it off-label for conditions like PCOS and sometimes during pregnancy—always after a discussion with your provider.

How to take metformin

Most people start low and increase slowly. Common starting doses are 500 mg once or twice daily with food to reduce stomach upset. There’s an extended-release form you take once daily. Typical maintenance doses range from 1500–2000 mg per day; some patients on close follow-up may reach about 2500 mg if needed and tolerated. Take pills with the largest meal, swallow whole, and keep a regular schedule—morning or evening both work depending on your routine.

Missed a dose? Take it when you remember unless it’s almost time for the next dose. Don’t double up. If you switch between immediate- and extended-release forms, check with your prescriber to match total daily dose and timing.

Side effects, monitoring, and interactions

Expect mild stomach issues at first—nausea, loose stools, and gas are common but usually fade in 2–4 weeks. Switching to extended-release often helps. Long-term use can lower vitamin B12 levels, so ask about a yearly B12 check if you’ve been on metformin for years or have symptoms like numbness or fatigue.

The rare but serious problem is lactic acidosis. It’s unlikely for most people but risk goes up if your kidneys are impaired, if you drink a lot of alcohol, or if you become dehydrated or very ill. Providers usually check kidney function (eGFR) before starting metformin and then every 6–12 months. Many avoid metformin if eGFR is below 30 mL/min/1.73 m² and use caution between 30–45.

Stop metformin around procedures that use iodinated contrast dye and restart only after kidney tests are back to normal. Tell every clinician you take metformin before surgery or new medicines. Heavy alcohol raises risk, so limit intake and discuss with your doctor.

Healthcare teams monitor fasting glucose, HbA1c, and kidney tests to see how well metformin is working. HbA1c goals vary by age and health—talk to your provider about yours. If blood sugar stays high, other medicines like SGLT2 inhibitors, GLP-1 receptor agonists, or insulin may be added.

Practical tips: store tablets at room temperature away from moisture, refill only from licensed pharmacies, and be cautious with very cheap online sellers. If you notice sudden severe belly pain, trouble breathing, extreme weakness, or a fast heartbeat, seek urgent care—those could be signs of a serious complication.

For everyday questions—how to manage side effects, when to test B12, or whether metformin can be combined with another diabetes drug—talk to your doctor or pharmacist. Small changes in dose or timing often fix common problems and keep treatment effective and safe.