During dehydration or acute illness, why is metformin often held?

• A. Because dehydration and acute illness raise the risk of lactic acidosis with metformin.
• B. Because metformin improves kidney function.
• C. Because it prevents ketone production.
• D. Because it is ineffective during illness.

Answer: (A)

Metformin is held during dehydration or acute illness because these conditions can raise the risk of lactic acidosis. Dehydration and illness often reduce kidney perfusion and oxygen delivery, which slows the clearance of metformin and increases lactate production. Metformin can potentiate lactic acid buildup when lactate isn’t cleared effectively, so stopping the medication in these situations helps prevent a harmful complication. It isn’t about improving kidney function or preventing ketone production, and the drug isn’t inherently ineffective during illness; the safety concern takes precedence, with therapy typically resumed after hydration and clinical stability have returned.