Metformin is the drug of choice for the treatment of type 2 diabetes and the basic therapeutic drug in the combination treatment program, applied in the clinic for more than 50 years, is currently one of the most widely used oral hypoglycemic drugs in the world. 2016 released a new version of “Metformin Clinical Application Expert Consensus”, the following is to introduce a few of the more concerned issues. 1, does metformin hurt the liver and kidneys? (1) Many diabetic patients worry that metformin hurts the liver and kidneys, and dare not take it, delaying the treatment. Metformin is not metabolized by the liver, no liver toxicity. However, severely impaired liver function will significantly limit the clearance of lactic acid, and it is recommended that patients with serum transaminases exceeding 3 times the upper limit of normal or with severe liver insufficiency should avoid using metformin. (2) Metformin itself does not have an effect on renal function, and some studies suggest that metformin may have a renal protective effect. There is a clinical misconception of discontinuing metformin use based on proteinuria alone. It is recommended that metformin be relaxed for use in patients with moderate renal insufficiency type 2 diabetes and be contraindicated only in patients with eGFR <30 mL/(min-1.73m2). 2.Does metformin have any effect on the absorption of vitamin B12? Some studies have shown that long-term metformin administration can cause a decrease in vitamin B12 levels. It is recommended that patients on long-term metformin therapy should be appropriately supplemented with vitamin B12, and it is not recommended that patients taking metformin should have their vitamin B12 levels routinely monitored. 3.Can it still be used in elderly patients over 65 years old? Domestic and international guidelines related to diabetes do not limit the specific age of metformin use. The reasonable application of metformin in elderly diabetic patients can achieve good hypoglycemic effect, and the less risk of hypoglycemia is also beneficial to elderly patients. 80 years old and above [except eGFR<30 mL/(min-1.73m2)] can still achieve good results with metformin if they have good indications and start from small doses, under reasonable monitoring conditions. Therefore, age is not a contraindication to metformin treatment, but regular monitoring of renal function is required. 4.Can metformin be used in children and adolescents with diabetes? Metformin can be used in children or adolescents with T2DM aged 10 years and above, and the highest dose should not exceed 2000mg/d. It is not recommended for children under 10 years old. 5.Can metformin be used in patients with gestational diabetes? Although several international academic organizations recommend metformin for use in patients with gestational diabetes mellitus, it is not recommended for the time being based on the lack of evidence in China. 6.Do I need to stop metformin before the imaging or general anesthesia? (1) For diabetic patients with normal renal function, it is not necessary to stop metformin before imaging, but it should be stopped for 48-72h after using contrast agent under the guidance of doctor, and the drug can be continued after the renal function is normal on review. (2) And for patients with abnormal renal function, metformin should be temporarily stopped 48h before using contrast agent and general anesthesia, and then it should be stopped for 48-72h, and the drug can be continued after the renal function results are normal. 7.What are the dosage forms of metformin? At present, there are mainly single-component metformin ordinary tablets, metformin extended-release tablets or capsules and metformin enteric-coated tablets or capsules at home and abroad. (1) Ordinary tablets dissolve faster in the stomach and have more gastrointestinal adverse reactions. Generally administered 2 to 3 times a day, preferably with or after meals, to reduce gastrointestinal discomfort. (2) Enteric tablets have the advantage of less stimulating effect on the upper gastrointestinal tract than ordinary tablets, which can not only reduce the adverse reactions in the gastrointestinal tract, especially in the upper gastrointestinal tract, but also reduce the loss and enzymatic digestion of the drug in the upper gastrointestinal tract and increase its bioavailability. Like regular tablets, the administration method of metformin enteric-coated tablets is also 3 times a day, except that enteric-coated tablets can be administered 0.5 h before meals. (3) The slow release rate of extended-release tablets/capsules reduces the gastrointestinal reactions after administration. It can be taken at dinner or immediately after meals, and administered once a day to improve patients' medication compliance, which is especially suitable for office workers and elderly patients with memory loss. 8.What dose is clinically effective? The minimum recommended dose of metformin is 500mg/d, and the best effective dose is 2000mg/d. The maximum recommended dosage of extended release dosage form is 2000mg/d, and the maximum recommended dosage of generic tablets available for adults is 2550mg/d.