Contraindications to metformin include decompensated heart failure, severe infections, drug allergies, metabolic acidosis, alcoholism and other special populations. Metformin is a hypoglycemic drug and is commonly used to treat type 2 diabetes mellitus that is poorly controlled by diet alone. Adverse reactions are nausea, vomiting, diarrhea, abdominal pain, loss of appetite, fatigue, dizziness, rash, etc. For those with renal dysfunction due to decompensated heart failure, acute myocardial infarction, sepsis, etc., metformin is contraindicated to prevent aggravation of the condition. This drug is also contraindicated for patients with congestive heart failure who need to be treated with medication as prescribed by the doctor on a daily basis, and for those who are accompanied by serious heart and lung diseases. In addition to the above contraindications, Metformin is also contraindicated in severe infections, hypersensitivity to Metformin, metabolic acidosis, alcoholism, and uncorrected vitamin B12 and folic acid deficiencies to prevent accidents. It is recommended that patients apply Metformin under the guidance of a physician, and should not use the drug indiscriminately or adjust the dosage on their own. If discomfort occurs after using the drug, it should be discontinued in time and informed to the doctor for treatment.