Which symptom reported by a client, alerts the practical nurse (PN) that a scheduled dose of hydrochlorothiazide may need to be withheld?

A. Nausea: Nonspecific; not an immediate reason to hold unless severe. B. Headache: Common but nonspecific; not priority for holding medication. C. Dizziness: May indicate hypotension or electrolyte imbalance - possible adverse effect needing assessment before administration. D. Nervousness: Uncommon effect; not typically a reason to withhold.