Normal plasma osmolality is: (A) 285-300 milliosmo/kg, (B) 310-340 milliosmo/kg, (C) 200-240 milliosmo/kg, (D) 160-180 milliosmo/kg
Answer is A. The normal value of plasma osmolality is 285-300 mosm/kg.Osmolality is measured with an osmometer based on the depression of the freezing point of the sample.Patients with deficiency of ADH (Central diabetes insipidus) or a decreased response to ADH (Nephrogenic diabetes insipidus) will excrete urine with osmolality less than 300 mosmols/kg.Ref: D M Vasudevan 7th edition Page no: 373