A nurse is caring for a client who has a new prescription for lithium carbonate. Prior to administering the first dose, which of the following laboratory values should the nurse evaluate?

A. Arterial blood gases: ABGs assess acid-base balance and respiratory status, which are not directly affected by lithium therapy. They are not required prior to initiating lithium. B. Total cholesterol: Lithium does not significantly impact lipid metabolism, so baseline cholesterol is not necessary before starting therapy. C. Thyroid hormones: Lithium can affect thyroid function and may cause hypothyroidism over time. Evaluating baseline thyroid hormone levels prior to therapy helps monitor for potential adverse effects and guides ongoing management. D. Hemoglobin: Lithium does not directly affect hemoglobin levels, so baseline hemoglobin measurement is not required for safe initiation of therapy.