Eating 2 metformin a day is generally not harmful, but there may be adverse reactions to the drug. Currently on the market metformin is divided into metformin tablets and metformin extended-release tablets, and a single tablet of up to 0.5g, 2 capsules a day of up to 1g, is still in the therapeutic dose of the drug, and the use of the doctor’s advice is generally not harmful. The maximum dose of metformin is 2.55g for 1 day, even if 1g of metformin is taken for 1 day, it is still within the reasonable dose. However, there are some adverse reactions to this drug, such as gastrointestinal reactions, other abnormal systemic reactions, affecting the absorption of vitamins, lactic acidosis and so on. 1. Gastrointestinal reactions: diarrhea, nausea, bloating, fatigue, dyspepsia, some patients stop taking the drug because of diarrhea. Other rare cases are abnormal stool, constipation, abdominal pain, abdominal distension. 2. Other abnormal systemic reactions: hypoglycemia, myalgia, dizziness, lightheadedness, nail abnormalities, skin rash, increased sweating, abnormal taste, chest discomfort, chills, flu symptoms, hot flashes, palpitations, and weight loss. 3. Affecting vitamin absorption: can reduce vitamin B12 absorption, but rarely cause anemia. 4. Lactic acidosis: Lactic acidosis is a very rare but serious (high mortality rate if untreated) metabolic complication, which can be induced by metformin accumulation in the body. However, its incidence is very low and usually occurs in patients with significant renal dysfunction. If any of the above adverse reactions occur while the patient is taking the drug, the drug should be discontinued and the patient should seek immediate medical attention.