A nurse is providing discharge teaching to a client who has bipolar disorder and will be discharged with a prescription for lithium. The nurse should teach the client that which of the following factors puts her at risk for lithium toxicity?

A. Drinking 2 liters of fluids daily is appropriate and helps maintain adequate hydration, which is important in preventing lithium toxicity. B. Foods high in tyramine interact with MAOIs, not lithium; this is not a relevant concern for lithium therapy. C. Consuming 2 to 3 grams of sodium daily is within the normal dietary range and supports stable lithium levels, as lithium and sodium compete for reabsorption in the kidneys. D. Running 4 miles outdoors daily can lead to excessive sweating and dehydration, which can concentrate lithium levels in the blood and increase the risk of toxicity. Adequate hydration and monitoring sodium loss are critical during heavy physical activity.