Normal Osmolality — FRCA Primary MCQ
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Correct answer: C — 275-295 mOsm/kg
Normal serum osmolality is 275-295 mOsm/kg determined primarily by sodium and associated anions. Calculated osmolality ≈ 2[Na+] + [urea] + [glucose] (mmol/L). Osmolar gap (measured - calculated) is normally <10 mOsm/kg.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist