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Osmolality, Urine
Test CodeOSMOU
Alias/See Also
Performed at Sonora Quest Laboratory, Test code 9295
Urine OSMO
Page and BCCH send to SQL
BGFMC to BIMC
WMC and TCH to WyMCC
BUMCS sends to BUMCT
All other locations perform on-site
Urine OSMO
Page and BCCH send to SQL
BGFMC to BIMC
WMC and TCH to WyMCC
BUMCS sends to BUMCT
All other locations perform on-site
CPT Codes
83935
Instructions
For facilities sending to Sonora Quest Laboratories, see link below for specimen details, methodology, setup schedule and reference ranges.
Clinical Significance
Osmolality is used to evaluate the concentrating ability of the tubules in the kidneys.
Low serum or plasma osmolality levels are seen in adrenocortical insufficiency, panhypopituitarism, water intoxication and
postoperative status, (especially with excessive water replacement therapy, syndrome of inappropriate ADH secretion).
High serum or plasma osmolality levels are seen with water depletion, hyper-osmolar, nonketotic diabetic coma, diabetic
ketoacidosis, hypernatremic ethanol intoxication, diabetes insipidus, hypercalcemia, cerebral lesions, and often with tube feeding.
Low urine osmolality levels are seen with diabetes insipidus and primary polydipsia. After fluid restriction of 12-14 hours, a patient
with normal renal function should be able to concentrate urine to at least 800 mOsm/kg. Loss of this function is seen in early renal
failure, and a concentration ability of only 400 mOsm/kg would indicate severe renal dysfunction.
The normal ratio of urine osmolality to serum osmolality is between 1.0 – 3.0. In patients with fluid restriction, the ratio is ≥3.0 and
may rise in extremes to 4.7. In renal tubular deficiency, the ratio is <3.0 and may rise in extremes to 4.7. In polyuria of diabetes
insipidus, the ratio will be 0.2 – 0.7.
Low serum or plasma osmolality levels are seen in adrenocortical insufficiency, panhypopituitarism, water intoxication and
postoperative status, (especially with excessive water replacement therapy, syndrome of inappropriate ADH secretion).
High serum or plasma osmolality levels are seen with water depletion, hyper-osmolar, nonketotic diabetic coma, diabetic
ketoacidosis, hypernatremic ethanol intoxication, diabetes insipidus, hypercalcemia, cerebral lesions, and often with tube feeding.
Low urine osmolality levels are seen with diabetes insipidus and primary polydipsia. After fluid restriction of 12-14 hours, a patient
with normal renal function should be able to concentrate urine to at least 800 mOsm/kg. Loss of this function is seen in early renal
failure, and a concentration ability of only 400 mOsm/kg would indicate severe renal dysfunction.
The normal ratio of urine osmolality to serum osmolality is between 1.0 – 3.0. In patients with fluid restriction, the ratio is ≥3.0 and
may rise in extremes to 4.7. In renal tubular deficiency, the ratio is <3.0 and may rise in extremes to 4.7. In polyuria of diabetes
insipidus, the ratio will be 0.2 – 0.7.
Additional Information
Osmolality, Urine
