Osmolality for Beginners
What is osmolality?
Osmolality is a highly effective means of determining
the total number of particles present in blood, urine, or other fluids.
Osmolality increases with dehydration and decreases with overhydration.
There are three types of osmolality tests: urine, plasma, and stool. Urine
osmolality is an important test for renal concentrating ability of the
kidney. Plasma (or serum) osmolality is a useful preliminary investigation
for identifying the cause of hyponatraemia. Stool or faecal osmolality
can be used to assist with diagnosis of the cause of diarrhea.