An outpatient diagnosed with bipolar disorder is prescribed lithium. The patient telephones the nurse to say, "I've had severe diarrhea for 4 days. I feel very weak and unsteady when I walk. My usual hand tremor has gotten worse. What should I do?" The nurse will advise the patient to

Rationale: A. Severe diarrhea, worsening tremor, weakness, and unsteady gait are signs of possible lithium toxicity, which requires immediate medical evaluation; the patient should be brought to the clinic promptly. B. Restricting fluids can worsen dehydration and increase lithium concentration, making toxicity more likely. C. Taking an antidiarrheal does not address the underlying problem and may delay urgent treatment. D. Adding salt and water will not reverse toxicity and could delay necessary medical intervention.