The nurse is evaluating a client's understanding of safety considerations related to metformin therapy. Which client statement indicates a need for further teaching?

The statement indicating a need for further teaching is that alcohol is acceptable as long as it is only on weekends. Metformin carries a risk of lactic acidosis, a rare but potentially fatal complication, and alcohol consumption significantly increases this risk by impairing lactate metabolism in the liver. Clients on metformin should avoid or strictly limit alcohol regardless of the frequency or timing. The statement about notifying the provider before contrast-dye imaging is correct because iodinated contrast media can cause acute kidney injury, which impairs metformin excretion and raises lactic acid levels; metformin is typically held before and after contrast procedures. Acknowledging that the medication may cause initial gastrointestinal upset — including nausea, diarrhea, and abdominal cramping — reflects correct understanding of metformin's most common side effect profile, which often improves over time or with food intake. Monitoring for muscle pain or weakness is appropriate because these can be early signs of lactic acidosis, warranting immediate reporting to the provider. All three of those statements reflect accurate understanding, making the alcohol statement the one that requires correction.