Metformin is one of the commonly used hypoglycemic medications and its use generally has no effect on the function of the thyroid gland. Metformin needs to be used as prescribed by the doctor. The main pharmacological effect of metformin is to reduce blood glucose by inhibiting hepatic glucose output, improving the sensitivity of peripheral tissues to insulin, and increasing the uptake and utilization of glucose. 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, combination with insulin may reduce insulin dosage and blood glucose fluctuations. Contraindications to metformin include type 2 diabetes mellitus combined with acute severe metabolic disorders, severe infections, hypoxia, trauma, major surgery, pregnant and lactating women, etc.; those who are allergic to the drug or have serious adverse reactions; and alcoholics. There is no evidence that Metformin has an effect on the thyroid gland, Metformin should be consulted with a medical professional before use.