Metformin belongs to the biguanide class of hypoglycemic drugs, which is an oral drug, and can reduce gastrointestinal reactions when taken during or immediately after meals. The specific dosage of metformin varies according to the drug form and the patient’s condition. Usually, the starting dose for adults is 0.25g once, 2~3 times a day, and the maximum daily dose should not exceed 2g. Metformin is used as a first-line drug in the treatment of type 2 diabetes, either alone or in combination with other drugs. When used in patients with type 1 diabetes mellitus, combination with insulin may reduce insulin dosage and blood glucose fluctuations. Note that the drug is contraindicated in type 2 diabetes mellitus combined with acute severe metabolic disorders, severe infections, hypoxia, trauma, major surgery, pregnant and lactating women. For different patients, the dosage of metformin treatment may be different, and patients need to visit the hospital in time and take the drug under the guidance of professional doctors.