What are the side effects of taking metformin?

Generally, common formulations of metformin include tablets, extended-release tablets, and capsules. Side effects of metformin may include gastrointestinal reactions, vitamin B12 deficiency, hypoglycemia, lactic acidosis, and allergic reactions. Details are as follows:

1. Gastrointestinal Reactions: Gastrointestinal reactions are the most common side effect of metformin. Many patients experience nausea, vomiting, diarrhea, reduced appetite, or indigestion when initially starting the medication or when the dosage is increased. These symptoms may gradually diminish with continued use. Patients can reduce these symptoms by taking the medication with meals and gradually increasing the dosage from a low starting level. If severe gastrointestinal reactions occur, such as severe diarrhea and vomiting accompanied by fever or other symptoms, the medication should be discontinued immediately and medical attention sought promptly.

2. Vitamin B12 Deficiency: Long-term use of metformin may lead to vitamin B12 deficiency, which can cause malnutrition and neurological complications. Vitamin B12 is crucial for maintaining normal nervous system function, and its deficiency may lead to early onset of diabetic complications such as numbness, pain in the lower limbs, and painless myocardial infarction. Therefore, patients should regularly monitor their vitamin B12 levels during metformin therapy and supplement when necessary.

3. Hypoglycemia: Metformin alone rarely causes hypoglycemia. However, when used in combination with insulin or insulin secretagogues, the risk of hypoglycemia increases. Therefore, patients should pay special attention to blood glucose monitoring when using these drug combinations and adjust dosages as needed to avoid hypoglycemia.

4. Lactic Acidosis: Lactic acidosis is a very serious but relatively rare side effect of metformin. This condition mainly occurs in patients with impaired kidney function or severe hypoxia. Symptoms include severe fatigue, rapid breathing, vomiting, diarrhea, or muscle cramps. Immediate medical attention is required upon the appearance of these symptoms, as lactic acidosis has a high mortality rate.

5. Allergic Reactions: A small number of patients may experience allergic reactions after using metformin, such as hives, difficulty breathing, rash, or swelling of the tongue and throat. Once these reactions occur, the medication should be stopped immediately, and appropriate medical management should be undertaken under a physician's guidance.

When using metformin, patients should strictly follow medical instructions for medication and regularly monitor blood glucose and related indicators. If any discomfort or suspected side effects occur, prompt medical attention should be sought, and the treating physician should be informed of all medications currently in use.