A diabetic client who is currently taking metformin is ordered a computerized tomography (CT) scan with contrast. The nurse understands that the client's metformin should be discontinued how many hours before receiving intravenous (IV) contrast?

A. Discontinuing metformin 24 hours before a CT scan is longer than necessary and not standard practice. B. It is generally recommended that metformin be held for at least 12 hours before the administration of IV contrast to reduce the risk of lactic acidosis, especially in clients with renal impairment. C. Six hours is insufficient time to ensure the medication is cleared from the system, considering the potential risks. D. Discontinuing metformin for 48 hours is overly cautious and not necessary unless there are complications that arise after the contrast is administered.