The most serious side effect of metformin is mainly the relatively rare lactic acidosis. Long-term use of metformin may reduce the absorption of vitamin B12, and if patients develop megaloblastic anemia, this cause should be considered at this time, but is generally very rare. Common adverse reactions are mainly digestive, such as nausea, vomiting, diarrhea, abdominal pain, and loss of appetite, and most patients can relieve themselves by stopping the administration of the drug. This drug will also have common ones, such as taste disturbance and abnormalities of the gastrointestinal tract. In addition, there will be some rare ones, such as subcutaneous tissue abnormalities, skin reactions, such as urticaria, erythema, itching and other symptoms, so you should read the instruction manual before using the drug and fully understand the drug before starting to use it to avoid intolerable reactions, but once intolerable reactions and symptoms occur, consult your pharmacist or go to the hospital.