Urine
osmolality
Molality is a measure of the number of moles of solute in a solution corresponding to 1 kg or 1000 g of solvent. This contrasts with the definition of molarity which is based on a specified volume of solution.
A commonly used unit for molali ...
is a measure of
urine
Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra.
Cel ...
concentration,
in which large values indicate concentrated urine and small values indicate diluted urine. Consumption of water (including water contained in food) affects the osmolality of urine.
[ ]
Osmolality is measured by osmometer, which evaluates the freezing point depression of a solution and supplies results as milliosmoles per kilogram of water while specific gravity is measured by colorimetric strips, refractometer, hydrometer and pyknometer.
In healthy humans with restricted fluid intake, urine osmolality should be greater than 800
mOsm
Osmotic concentration, formerly known as osmolarity, is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/L ...
/kg, while a 24-hour urine osmolality should average between 500 and 800 mOsm/kg.
Urine osmolality in humans can range from approximately 50 to 1200 mOsm/kg, depending on whether the person has recently drunk a large quantity of water (the lower number) or has gone without water for a long time (the higher number).
Plasma osmolality with typical fluid intake often averages approximately 290 mOsm/kg H
2O in humans.
In other animals
Some mammals are capable of higher osmolality than humans. This includes rats (approximately 3,000 mOsm/kg H
2O), hamsters and mice (approximately 4,000 mOsm/kg H
2O), and chinchillas (approximately 7,600 mOsm/kg H
2O)
See also
*
Plasma osmolality
Plasma osmolality measures the body's electrolyte–water balance. There are several methods for arriving at this quantity through measurement or calculation.
Osmolality and osmolarity are measures that are technically different, but functional ...
References
Urine
Human physiology
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