Known brand names include Glucophage, Glumetza, and Riomet.
A pill for type 2 diabetes, used with diet and exercise. It lowers blood sugar mainly by making the liver release less glucose, and it does not cause low blood sugar on its own.
First-line. Common first-line oral therapy for type 2 diabetes, with diet and exercise.
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Long the default first drug for type 2 diabetes: effective, inexpensive, weight neutral, and low in hypoglycemia risk alone. Current guidelines also weigh cardiovascular, heart failure, and kidney comorbidities, which may favor adding or starting an SGLT2 inhibitor or GLP-1 receptor agonist. Avoid when eGFR is below 30, with hepatic disease, or when lactic acidosis risk is high.
A biguanide. It cuts glucose output from the liver, reduces glucose absorption from the gut, and improves insulin sensitivity so muscle takes up more glucose. Insulin secretion does not increase.
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The label does not describe a narrow therapeutic index or direct dosing by measured blood levels of the drug.
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Doses come from the FDA label. Study tool, not for clinical decisions.
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Check eGFR before starting and at least yearly. Below 30: contraindicated. 30 to 45: do not start. If eGFR falls below 45 on therapy, weigh benefit against risk; stop if it falls below 30.
Lactic acidosis. Rare but can be fatal, with a subtle onset of malaise, myalgias, breathing trouble, sleepiness, and abdominal pain. Risk rises with renal impairment, age 65 or older, iodinated contrast, surgery, hypoxic states, heavy alcohol use, hepatic impairment, and drugs such as topiramate. If suspected, stop metformin, give supportive care in hospital, and start hemodialysis promptly.
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Published studies have not shown a clear link to major birth defects or miscarriage, though data are limited. Poorly controlled diabetes in pregnancy carries real risks for mother and fetus.
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Present in human milk in small studies. Effects on the infant are not well defined, so weigh the benefits of breastfeeding against the mother's need for the drug.
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Type 2 diabetes from age 10: start 500 mg twice daily with meals, increasing by 500 mg weekly to at most 2,000 mg per day in two doses. Not established under age 10.