This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Which of the following is a serious and characteristic adverse effect of Metformin \nSelect and explain. \nA. Lactic acidosis, B. Weight gain, C. Hypoglycemia, D. Dilutional hyponatremia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: A. Lactic acidosis [Ref: KDT 7h/e p. 453).Two impoant adverse effects of these agents are lactic acidosis (more with phenformin) and vitamin B12 deficiency (more common with metformin).More common side effects are abdominal pain, anorexia, metallic taste, mild diarrhea and tiredness.', 'role': 'assistant'}]