A client is prescribed metformin for type 2 diabetes. Which instruction is MOST important to include in patient teaching?

Metformin patient teaching priorities:

With food: Taking with meals significantly reduces GI side effects (nausea, diarrhea, abdominal discomfort) that cause many patients to discontinue.

Lactic acidosis: Rare but serious adverse effect; early symptoms: unusual muscle pain, weakness, difficulty breathing, stomach discomfort, dizziness, unusual sleepiness; risk increased with renal impairment — metformin is contraindicated with eGFR below 30.

Contrast/surgery hold: Metformin must be HELD 48 hours before IV contrast (risk of contrast-induced nephropathy with metformin = increased lactic acidosis risk) and any major surgery; resume after renal function confirmed normal 48 hours post-procedure.

Hypoglycemia: Metformin alone does NOT cause hypoglycemia (it reduces hepatic glucose production without stimulating insulin release) — this distinguishes it from sulfonylureas.

Monitoring: BMP/CMP for renal function monitoring; HbA1c every 3-6 months.