Taking metformin will have a feeling of nausea, the main common side effects of metformin are gastrointestinal reactions, including nausea, vomiting, diarrhea, abdominal pain, etc., so previous gastrointestinal disease is not recommended to apply metformin. Some patients can gradually tolerate it after taking it for a few days, while others cannot. It is recommended to start with a small dose, gradually increase the dose, and choose to take it orally after meals or with meals, which can effectively reduce the adverse reactions in the digestive tract. For those who really can not tolerate can only change the glucose-lowering drugs or choose insulin for glucose-lowering treatment, note that elderly patients in the application of metformin glucose lowering must be careful, regular monitoring of the level of liver and kidney function, in addition, before and after iodine contrast examination, should be suspended at least forty-eight hours to take metformin.