Etymology: Gk, hypo + osmos, impulse
a state or condition of abnormally reduced osmolality. The normal serum concentration (millimoles per liter) is 0.43-0.50 times the serum osmolality (milliosmoles per kilogram). A decrease in this ratio is caused by an increase in other osmolutes such as glucose or ketone bodies in diabetes mellitus, urea in uremia, or salicylate in salicylic poisoning. See also osmolality.